MCP server · registry snapshot 2026-10-23 · last tested 2026-10-23

ai.zerowidth/caliper

Build datasets and rubrics, then run evals that score your AI in Caliper. — the publisher's description

1 of 2 record checks metRead-only · tools listed 2026-10-23Topic: ai-and-ml · AI-classifiedPricing: freemium · AI-classifiedversion 1.0.0streamable HTTP45 tools

Summary

ai.zerowidth/caliper is a remote MCP server listed in the official MCP registry at version 1.0.0. On 2026-10-23 ProtocolProbe connected to it in read-only mode and read its inventory: 45 tools, 134 resources and 0 prompts.

Record checks

1 of 2 record checks met · 7 do not apply

met: Registry entry is active and says how to run it
not met: Source repository link opens
not applicable: Repository is not archived
not applicable: Code pushed to the repository in the 90 days before our check
not applicable: Repository publishes a security policy (SECURITY.md)
not applicable: Package names its licence with a standard (SPDX) identifier
not applicable: The version the registry lists can be installed and is not withdrawn
not applicable: npm package carries build provenance (attestation)
not applicable: No known critical or high advisory in the package or its dependencies

Not ranked by downloads: a remote server publishes no download figure
Not ranked by stars: no public GitHub repository

From public records, not a safety rating. Each check with its reason · Is it safe to install?

Key facts

Runs: remote (hosted by the publisher)
Transport: streamable HTTP
Sign-in: none needed to open a session
Tools: 45
Described as changing data: 20 of 45 toolsAI-classified
Topic: ai-and-mlAI-classified
Pricing: freemiumAI-classified
Last tested: 2026-10-23

Add to your client

Observed fact

This server accepted a session without any credential and lists 17 tools whose name or declaration suggests they change data (caliper_datasets_update, caliper_datasets_delete, caliper_datasets_update_item, caliper_datasets_remove_item, caliper_rubrics_update and 12 more). That is our reading of the names; we did not call them. Source: our connection, 2026-10-23.

Worth knowing before you connect it

20 tools are described as changing something (caliper_datasets_update, caliper_datasets_delete, caliper_datasets_update_item, …): our AI model's reading of the descriptions, not something we tested, and the server opened a session without any credential. We did not call them.

Each line comes from a section below, with its source and date.

How fresh this is

Live-tested: yes, a real session (not a text-only review)
Last tested: 2026-10-23
Mode: read-only (no tool calls)
Latest version: 1.0.0, published 2026-10-07 (registry, as of the 2026-10-23 snapshot)
First listed version: 2026-10-07 (earliest version still in the registry; older removed versions would be earlier)
Registry data: snapshot 2026-10-23
Package and repository: checked 2026-10-22
Engine: mcp-runtime-engine@0.1.0 · sdk@1.32.0

Changes since the last refresh

New in the registry: not in the list of 2026-10-04, listed on 2026-10-23 with version 1.0.0 (published 2026-10-07).

Source: the official MCP Registry list on 2026-10-04 and on 2026-10-23.

What it is

What does this server offer?

Observed inventory

45tools

134resources

0prompts

20 of 45 tools are described as changing something (creating, editing, deleting, sending or running). For 5 the reading was uncertain, so no mark is shown.

search_docson 140 other serversreads or searches
“Search ZeroWidth product documentation.”
Publisher declares: read-only yes · destructive no · open-world no
2 inputs, 1 required
- querystringrequired“Search query — keywords or natural-language phrase.”
- limitinteger“Max number of results.”
get_docon 42 other serversreads or searches
“Fetch the full Markdown body of a specific docs page by its slug.”
Publisher declares: read-only yes · destructive no · open-world no
1 input, 1 required
- slugstringrequired“Page slug.”
list_docson 31 other serversreads or searches
“Enumerate all available docs pages, optionally filtered by product (e.g.”
Publisher declares: read-only yes · destructive no · open-world no
1 input
- productstring“Optional product slug filter (e.g.”
caliper_datasets_getreads or searches
“One dataset with a page of its items — read this BEFORE editing items (caliper_datasets_update_item needs the item id) and before extending coverage, so you don't add cases that already exist.”
Publisher declares: read-only yes · destructive no · open-world no
4 inputs, 1 required
- datasetIdstringrequired“Dataset id, from caliper_datasets_list.”
- limitinteger“Items per page, 1-100.”
- offsetinteger“Items to skip.”
- workspacestring“Workspace slug.”
caliper_datasets_updatecreates or changes datadescribed as changing data
“Changes a dataset's title, description, or visibility.”
Publisher declares: read-only no · destructive yes · open-world no
6 inputs, 1 required
- datasetIdstringrequired“Dataset id, from caliper_datasets_list.”
- titlestring“New name.”
- descriptionstring or null“New description; null clears it.”
- visibilitystring“Who can see it: PRIVATE (only the user), WORKSPACE (every member, the default), or SHARED (specific people, granted afterwards).”
- workspacestring“Workspace slug.”
- approvalIdstring“Approval id from a prior needs_confirmation response.”
caliper_datasets_deletedeletesdescribed as changing data
“Deletes a dataset.”
Publisher declares: read-only no · destructive yes · open-world no
3 inputs, 1 required
- datasetIdstringrequired“Dataset id, from caliper_datasets_list.”
- workspacestring“Workspace slug.”
- approvalIdstring“Approval id from a prior needs_confirmation response.”
caliper_datasets_update_itemcreates or changes datadescribed as changing data
“Rewrites one item's content, keeping its id (ratings and eval results keyed to it stay attached).”
Publisher declares: read-only no · destructive yes · open-world no
5 inputs, 3 required
- datasetIdstringrequired“Dataset id.”
- itemIdstringrequired“Item id, from caliper_datasets_get.”
- itemobjectrequired“The full replacement item, same four shapes as caliper_datasets_create.”
- workspacestring“Workspace slug.”
- approvalIdstring“Approval id from a prior needs_confirmation response.”
caliper_datasets_remove_itemdeletesdescribed as changing data
“Drops one item.”
Publisher declares: read-only no · destructive yes · open-world no
4 inputs, 2 required
- datasetIdstringrequired“Dataset id.”
- itemIdstringrequired“Item id, from caliper_datasets_get.”
- workspacestring“Workspace slug.”
- approvalIdstring“Approval id from a prior needs_confirmation response.”
caliper_datasets_generategenerates contentdescribed as changing data
“Creates a NEW dataset of model-written items — Q&A by default, or scripted sequences / simulated people via `shape` — pass flowId and the generator reads the flow's prompt, mode, and schema to write …”
Publisher declares: read-only no · destructive no · open-world no
13 inputs, 1 required
- titlestringrequired“Dataset name.”
- flowIdstring“Workbench flow to generate cases for (from workbench_flows_list).”
- descriptionstring“What the target system does / what to cover.”
- countinteger“Items to generate, 1-50.”
- shapestring“What each generated item is: `qa` (one input, the default), `sequence` (2-6 scripted user turns the model answers one at a time, with expectedResponse + expect…”
- dispositionstring“With shape `simulated`: how every generated person behaves — a preset id (genuine, pressure, confused, impatient, vague, non-native) or free text.”
- outputsModestring“What each generated item carries beyond the input: `expected` (golden answers — eval-ready, the default), `none` (inputs only — for a spec others fill in), `ca…”
- expectedStylestring“With outputsMode `expected`: `verbatim` literal reference answers (default) or `conditions` — what a correct answer must do, when there's no single right wordi…”
- presetIdstring“Framing preset.”
- datasetDescriptionstring“Description stored on the dataset.”
- visibilitystring“Who can see it: PRIVATE (only the user), WORKSPACE (every member, the default), or SHARED (specific people, granted afterwards).”
- workspacestring“Workspace slug.”
- approvalIdstring“Approval id from a prior needs_confirmation response.”
caliper_datasets_generate_itemsgenerates contentdescribed as changing data
“Appends model-written items to an EXISTING dataset, in the style of what's already there (existing items are the few-shot examples; the output shape matches theirs unless overridden).”
Publisher declares: read-only no · destructive no · open-world no
10 inputs, 1 required
- datasetIdstringrequired“Dataset to extend, from caliper_datasets_list.”
- countinteger“Items to add, 1-20.”
- descriptionstring“What to bias toward, e.g.”
- shapestring“What each generated item is: `qa` (one input, the default), `sequence` (2-6 scripted user turns the model answers one at a time, with expectedResponse + expect…”
- dispositionstring“With shape `simulated`: how every generated person behaves — a preset id (genuine, pressure, confused, impatient, vague, non-native) or free text.”
- outputsModestring“What each generated item carries beyond the input: `expected` (golden answers — eval-ready, the default), `none` (inputs only — for a spec others fill in), `ca…”
- expectedStylestring“With outputsMode `expected`: `verbatim` literal reference answers (default) or `conditions` — what a correct answer must do, when there's no single right wordi…”
- anchorItemIdstring“An item id (from caliper_datasets_get) the new items should resemble most.”
- workspacestring“Workspace slug.”
- approvalIdstring“Approval id from a prior needs_confirmation response.”
caliper_rubrics_listreads or searches
“Lists the rubrics in the active workspace (id, name, description, criterion count).”
Publisher declares: read-only yes · destructive no · open-world no
1 input
- workspacestring“Workspace slug.”
caliper_rubrics_getreads or searches
“One rubric with its criteria — each criterion's name, what the judge looks for, and the score scale.”
Publisher declares: read-only yes · destructive no · open-world no
2 inputs, 1 required
- rubricIdstringrequired“Rubric id.”
- workspacestring“Workspace slug.”

Show 33 more tools

caliper_rubrics_updatecreates or changes datadescribed as changing data
“Changes a rubric's title, description, visibility, or replaces its criteria wholesale (pass the FULL list — criteria get fresh ids).”
Publisher declares: read-only no · destructive yes · open-world no
7 inputs, 1 required
- rubricIdstringrequired“Rubric id, from caliper_rubrics_list.”
- titlestring“New name.”
- descriptionstring or null“New description; null clears it.”
- visibilitystring“Who can see it: PRIVATE (only the user), WORKSPACE (every member, the default), or SHARED (specific people, granted afterwards).”
- criteriaarray“Replacement criteria (1-10) — the whole list, not a diff.”
- workspacestring“Workspace slug.”
- approvalIdstring“Approval id from a prior needs_confirmation response.”
caliper_rubrics_deletedeletesdescribed as changing data
“Deletes a rubric.”
Publisher declares: read-only no · destructive yes · open-world no
3 inputs, 1 required
- rubricIdstringrequired“Rubric id, from caliper_rubrics_list.”
- workspacestring“Workspace slug.”
- approvalIdstring“Approval id from a prior needs_confirmation response.”
caliper_evals_getreads or searches
“One eval: what it targets (Workbench flow + stage, or external), its dataset and rubric ids, the rubric criteria it scores with (the snapshot taken at creation), schedule + runOnPublish + regression …”
Publisher declares: read-only yes · destructive no · open-world no
2 inputs, 1 required
- evalIdstringrequired“Eval id.”
- workspacestring“Workspace slug.”
caliper_evals_runs_item_executionreads or searches
“What the flow actually DID on one run item: every step in order (what it said, which tools it called with what arguments, what came back) and the final answer, plus status, duration, and cost.”
Publisher declares: read-only yes · destructive no · open-world no
4 inputs, 3 required
- evalIdstringrequired“Eval the run belongs to.”
- runIdstringrequired“Run id.”
- runItemIdstringrequired“The run item's `id` from caliper_evals_runs_get (not its dataset itemId).”
- workspacestring“Workspace slug.”
caliper_evals_updatecreates or changes datadescribed as changing data
“Changes an eval's title, description, visibility, schedule (interval + time anchor), runOnPublish (queue a run whenever the flow publishes), regressionThreshold (score drop vs the previous run that t…”
Publisher declares: read-only no · destructive yes · open-world no
13 inputs, 1 required
- evalIdstringrequired“Eval id, from caliper_evals_list.”
- titlestring“New name.”
- descriptionstring or null“New description; null clears it.”
- visibilitystring“Who can see it: PRIVATE (only the user), WORKSPACE (every member, the default), or SHARED (specific people, granted afterwards).”
- scheduleIntervalstring or null“Run cadence; null clears the schedule.”
- scheduleTimestring or null“Daily/weekly anchor, HH:MM 24-hour in scheduleTimezone.”
- scheduleTimezonestring or null“IANA timezone for scheduleTime, e.g.”
- scheduleDayOfWeekinteger or null“Weekly only: 0 = Sunday … 6 = Saturday.”
- runOnPublishboolean“Run whenever the targeted flow publishes a version.”
- regressionThresholdnumber or null“Score drop vs the previous run that raises an alert, on the 0–1 score scale (0.1 = 10 points); null turns alerts off.”
- scenarioIdstring or null“Workbench-flow evals: the scenario every run uses unless a run picks another (one of the flow's, from workbench_flows_scenarios_list); null clears it.”
- workspacestring“Workspace slug.”
- approvalIdstring“Approval id from a prior needs_confirmation response.”
caliper_evals_deletedeletesdescribed as changing data
“Deletes an eval and stops its schedule.”
Publisher declares: read-only no · destructive yes · open-world no
3 inputs, 1 required
- evalIdstringrequired“Eval id, from caliper_evals_list.”
- workspacestring“Workspace slug.”
- approvalIdstring“Approval id from a prior needs_confirmation response.”
caliper_evals_runs_canceldescribed as changing data
“Stops a run that is still PENDING / RUNNING / SCORING — the brake on a run that's spending more than expected or was started by mistake.”
Publisher declares: read-only no · destructive yes · open-world no
4 inputs, 2 required
- evalIdstringrequired“Eval the run belongs to.”
- runIdstringrequired“Run id, from caliper_evals_run or caliper_evals_runs_list.”
- workspacestring“Workspace slug.”
- approvalIdstring“Approval id from a prior needs_confirmation response.”
caliper_sources_listreads or searches
“Apps sending their agent's traces to Caliper — from their own code, OpenTelemetry, or a published Workbench flow — busiest first: name, how it sends, traces in the last 14 days (per day), and the too…”
Publisher declares: read-only yes · destructive no · open-world no
1 input
- workspacestring“Workspace slug.”
caliper_sources_over_timereads or searches
“One source day by day: traces, failures, tool calls, lookups that found nothing, tokens, cost, and speed (meanMs; p50/p95 as 'answered within' bucket edges); each tool with its calls and the share of…”
Publisher declares: read-only yes · destructive no · open-world no
3 inputs, 1 required
- sourceIdstringrequired“Source id, from caliper_sources_list or search_workspace.”
- daysinteger“How many days back, default 30.”
- workspacestring“Workspace slug.”
caliper_traces_listreads or searches
“The traces behind a point on a source's chart, newest first, 50 a page: the question and answer (cut short), tools called, time, tokens, cost, status.”
Publisher declares: read-only yes · destructive no · open-world no
7 inputs, 1 required
- sourceIdstringrequired“Source id, from caliper_sources_list or search_workspace.”
- daystring“One UTC day, YYYY-MM-DD.”
- toolstring“Only traces that called this tool.”
- documentstring“Only traces whose lookups hit this document.”
- errorsOnlyboolean“Only failed traces.”
- beforestring“Paging: the nextBefore from the previous page.”
- workspacestring“Workspace slug.”
caliper_traces_getreads or searches
“One trace: what came in, what went out, and every step in order — model calls (model, tokens, cost, reasoning), tool calls (arguments and result), lookups (query and documents with scores), anything …”
Publisher declares: read-only yes · destructive no · open-world no
3 inputs, 2 required
- sourceIdstringrequired“Source id, from caliper_sources_list or search_workspace.”
- traceIdstringrequired“Trace id, from caliper_traces_list.”
- workspacestring“Workspace slug.”
caliper_source_feeds_listreads or searches
“Datasets this source keeps adding to as conversations arrive: which dataset, for what (review, eval, spec), the pick it matches, sampling, how many have landed, and whether it's still running or why …”
Publisher declares: read-only yes · destructive no · open-world no
2 inputs, 1 required
- sourceIdstringrequired“Source id, from caliper_sources_list or search_workspace.”
- workspacestring“Workspace slug.”
caliper_sources_to_datasetcreates or changes datadescribed as changing data
“Saves the conversations behind a pick (a day, a tool, a document, failures — the same narrowing as caliper_traces_list) into a new dataset (newDatasetName) or an existing one (datasetId), newest firs…”
Publisher declares: read-only no · destructive no · open-world no
12 inputs, 2 required
- sourceIdstringrequired“Source id, from caliper_sources_list or search_workspace.”
- daystring“One UTC day, YYYY-MM-DD.”
- toolstring“Only traces that called this tool.”
- documentstring“Only traces whose lookups hit this document.”
- errorsOnlyboolean“Only failed traces.”
- purposestringrequired“review | eval | spec.”
- limitinteger“Most recent N, default 100.”
- datasetIdstring“Add to this dataset…”
- newDatasetNamestring“…or start one with this name.”
- keepAddingnumber“Keep adding new matches as they arrive, taking one in this many (1 = every one).”
- workspacestring“Workspace slug.”
- approvalIdstring“Approval id from a prior needs_confirmation response.”
caliper_source_feeds_stopdeletesdescribed as changing data
“Stops a source from adding new conversations to a dataset.”
Publisher declares: read-only no · destructive yes · open-world no
4 inputs, 2 required
- sourceIdstringrequired“Source id, from caliper_sources_list or search_workspace.”
- feedIdstringrequired“Live dataset id, from caliper_source_feeds_list.”
- workspacestring“Workspace slug.”
- approvalIdstring“Approval id from a prior needs_confirmation response.”
caliper_starters_listreads or searches
“The starter sets Caliper ships: prompt injection, system-prompt leaking, over-refusal, personal-data handling, bias under ambiguity.”
Publisher declares: read-only yes · destructive no · open-world no
Takes no inputs.
caliper_starters_installcreates or changes datadescribed as changing data
“Copies one starter into the workspace as a new dataset and a new rubric the user owns and can edit.”
Publisher declares: read-only no · destructive no · open-world no
3 inputs, 1 required
- slugstringrequired“Starter slug from caliper_starters_list.”
- workspacestring“Workspace slug override.”
- approvalIdstring“Approval id from a prior needs_confirmation response.”
caliper_datasets_listreads or searches
“Lists datasets in the active workspace.”
Publisher declares: read-only yes · destructive no · open-world no
1 input
- workspacestring“Workspace slug.”
caliper_flow_performancereads or searches
“How a Workbench flow is ACTUALLY doing, with receipts: every Caliper eval targeting the flow, recent runs with scores, the latest run decomposed into per-criterion averages, the score delta vs the pr…”
Publisher declares: read-only yes · destructive no · open-world no
2 inputs, 1 required
- flowIdstringrequired“Workbench flow id to report on.”
- workspacestring“Workspace slug.”
caliper_evals_runs_listreads or searches
“Recent runs for one eval, newest first: status (PENDING/RUNNING/SCORING/DONE/FAILED), overall score once DONE, label, and timestamps.”
Publisher declares: read-only yes · destructive no · open-world no
2 inputs, 1 required
- evalIdstringrequired“Eval whose runs to list.”
- workspacestring“Workspace slug.”
caliper_evals_runs_getreads or searches
“One run: status, overall score, and by default the ten lowest-scoring items with their per-criterion scores and the judge's reasoning (`items: all` for every item, `none` for totals only).”
Publisher declares: read-only yes · destructive no · open-world no
5 inputs, 2 required
- evalIdstringrequired“Eval the run belongs to.”
- runIdstringrequired“Run id, from caliper_evals_runs_list or caliper_evals_run.”
- itemsstring“Which items to include.”
- limitinteger“How many items for `worst`, default 10.”
- workspacestring“Workspace slug.”
caliper_evals_listreads or searches
“Lists evals in the active workspace with their target config (which Workbench flow, which dataset/rubric).”
Publisher declares: read-only yes · destructive no · open-world no
1 input
- workspacestring“Workspace slug.”
caliper_evals_runruns code or commandsdescribed as changing data
“Queues a new run of an eval — inference over the dataset, then LLM-judge scoring.”
Publisher declares: read-only no · destructive no · open-world yes
5 inputs, 1 required
- evalIdstringrequired“Eval to run.”
- labelstring“Short label for the run, e.g.”
- scenarioIdstring or null“Run as this scenario instead of the eval's own (one of the flow's, from workbench_flows_scenarios_list); null runs with none.”
- workspacestring“Workspace slug.”
- approvalIdstring“Approval id from a prior needs_confirmation envelope.”
caliper_datasets_createcreates or changes datadescribed as changing data
“Creates a dataset of test items — THE FIRST STEP of setting up evaluation for a flow.”
Publisher declares: read-only no · destructive no · open-world no
6 inputs, 2 required
- visibilitystring“Who can see it: PRIVATE (only the user), WORKSPACE (every member, the default), or SHARED (specific people, granted afterwards).”
- titlestringrequired“Dataset name (2-120 chars).”
- descriptionstring“What this dataset covers.”
- itemsarrayrequired“Test items (1-100).”
- workspacestring“Workspace slug.”
- approvalIdstring“Approval id from a prior needs_confirmation response.”
caliper_datasets_add_itemscreates or changes datadescribed as changing data
“Appends items to an existing dataset — use this to grow coverage (new edge cases, scenarios from a completed interview) instead of creating a parallel dataset.”
Publisher declares: read-only no · destructive no · open-world no
4 inputs, 2 required
- datasetIdstringrequired“Id of the dataset to extend.”
- itemsarrayrequired“Items to append (1-100).”
- workspacestring“Workspace slug.”
- approvalIdstring“Approval id from a prior needs_confirmation response.”
caliper_rubrics_createcreates or changes datadescribed as changing data
“Creates the scoring rubric an eval's LLM judge uses — 1-10 criteria, each scored on a numeric scale (default 1-5), judged pass/fail (kind pass_fail), or checked in code with no judge (kind check: con…”
Publisher declares: read-only no · destructive no · open-world no
6 inputs, 2 required
- visibilitystring“Who can see it: PRIVATE (only the user), WORKSPACE (every member, the default), or SHARED (specific people, granted afterwards).”
- titlestringrequired“Rubric name (2-120 chars).”
- descriptionstring
- criteriaarrayrequired
- workspacestring“Workspace slug override.”
- approvalIdstring“Approval id from a prior needs_confirmation response.”
caliper_evals_createcreates or changes datadescribed as changing data
“Binds a dataset + rubric to something under test as a repeatable eval — THE LAST SETUP STEP before scoring.”
Publisher declares: read-only no · destructive no · open-world no
13 inputs, 3 required
- visibilitystring“Who can see it: PRIVATE (only the user), WORKSPACE (every member, the default), or SHARED (specific people, granted afterwards).”
- titlestringrequired“Eval name (2-120 chars).”
- descriptionstring
- datasetIdstringrequired“Dataset of test items.”
- rubricIdstringrequired“Rubric the judge scores with.”
- targetstring“'workbench_flow' (default; needs flowId) or 'external' (the user's own model; outputs arrive through the public API).”
- externalLabelstring“External evals only: what produces the outputs, e.g.”
- flowIdstring“Workbench flow id to evaluate.”
- flowStagestring“Which stage to run against.”
- flowRevisionIdstring“Published-stage evals only: pin to one published revision (id from workbench_flows_revisions_list).”
- scenarioIdstring“Workbench-flow evals: run every item as this scenario (one of the flow's, from workbench_flows_scenarios_list), so the flow's variables hold that person's valu…”
- workspacestring“Workspace slug override.”
- approvalIdstring“Approval id from a prior needs_confirmation response.”
comments_liston 6 other serversreads or searches
“Lists the comment threads on one workspace entity (open first, then resolved) with authors and timestamps.”
Publisher declares: read-only yes · destructive no · open-world no
3 inputs, 2 required
- entityKindstringrequired“What the thread hangs on.”
- entityIdstringrequired
- workspacestring“Workspace slug.”
comments_createon 5 other serversdescribed as changing data
“Posts a comment on a workspace entity — a new thread, or a reply when rootId is given.”
Publisher declares: read-only no · destructive no · open-world no
7 inputs, 3 required
- entityKindstringrequired“What the thread hangs on.”
- entityIdstringrequired
- bodystringrequired
- rootIdstring“Reply into this thread; omit to start a new one.”
- mentionedUserIdsarray
- workspacestring“Workspace slug.”
- approvalIdstring
comments_resolveon 5 other servers
“Sets a comment thread's resolved state (rootId = the thread's root comment id).”
Publisher declares: read-only no · destructive yes · open-world no
4 inputs, 2 required
- rootIdstringrequired
- resolvedbooleanrequired
- workspacestring“Workspace slug.”
- approvalIdstring
search_workspaceon 10 other servers
“Finds anything in the workspace in one call — uploaded files (searching the text inside them), folders, Workbench flows, shims, knowledge bases and tasks, Compass pages and changes, Caliper datasets,…”
Publisher declares: read-only yes · destructive no · open-world no
5 inputs, 1 required
- qstringrequired“Words, any order, case-insensitive.”
- kindsarray“Restrict to these kinds (file, folder, flow, page, doc, dataset, …).”
- folderIdstring“Only search inside this folder and the folders under it (ids from workspace_folders_browse or a folder hit).”
- limitinteger
- workspacestring“Workspace slug.”
entity_tags_geton 5 other servers
“Returns the tags on a batch of entities of one kind — the labels galleries organize by.”
Publisher declares: read-only yes · destructive no · open-world no
3 inputs, 2 required
- entityKindstringrequired“Which kind the ids belong to.”
- idsarrayrequired
- workspacestring“Workspace slug.”
entity_tags_browseon 5 other servers
“Without a tag: every tag in use across the workspace with how many entities carry it, most-used first — the vocabulary the team already organizes by.”
Publisher declares: read-only yes · destructive no · open-world no
2 inputs
- tagstring“A tag to expand into its items.”
- workspacestring“Workspace slug.”
entity_tags_seton 5 other servers
“Replaces the FULL tag set on one entity (an empty list clears it).”
Publisher declares: read-only no · destructive yes · open-world no
5 inputs, 3 required
- entityKindstringrequired
- entityIdstringrequired
- tagsarrayrequired
- workspacestring“Workspace slug.”
- approvalIdstring“Approval id from a prior needs_confirmation response.”

Each quoted sentence is the first sentence of the publisher’s own description. The kind of tool and the “changes data” mark are our AI model’s reading of that description, not something we tested: two differently worded runs had to agree, otherwise no label is shown, and nobody has checked them by hand. A tool without the “changes data” mark is described as only reading, searching or calculating, or the two runs did not agree. No tool was called. Read the publisher’s full description before relying on it. “Publisher declares” lists the hints the server itself sends with the tool (MCP annotations: read-only, destructive, idempotent, open-world); they are the publisher's claims, not checked by us. Inputs are the parameters in the tool's own input schema: name, declared type, whether it is required, and the first sentence of its description. Read 2026-10-23.

How well are its tools described?

Features #4 and #5

How clearly this server's own tool descriptions say what a tool does, and how consistent its tool list is. The first part is an AI model's yes/no reading of each description; the second part is counted. We do not turn it into a grade.

Descriptions

AI reading of each description

Says what the tool does: 100% of 40 tools
Says what it returns: 100% of 31 tools
States limits, defaults or errors: 21% of 38 tools
Says when to use it: 100% of 17 tools
Items covered per tool: 3.2 of 4 on average

Counted from the listing

Parameters with a description: 92% of 197
Tools with a description: 100% of 45
Typical description length: 404 characters

The tool set

Counted from the listing

Tools: 45
Size of the list: about 17,944 tokens for an agent to load (characters ÷ 4)
Naming: 45 of 45 names use snake_case

AI reading: easy to mix up

search_docs and get_doc

The AI items cover 40 of 45 tools: for a tool where two differently worded runs disagreed, that item is left out. They were not checked by hand, and no tool was called. “Easy to mix up” means two tools whose names or descriptions overlap without saying how they differ; the AI found these, comparing tools within groups of 40. We do not rate whether the tool set is complete or whether side effects are spelled out, because our AI reading of those was not reliable enough.

How do I add it to my client?

Config from the registry entry

From the remote endpoint (Streamable HTTP)

We connected to this URL on 2026-10-23 (a read-only session: no tool was called).

Add to CursorAn install link in the format Cursor documents, holding the Cursor config below.

Claude Desktop or claude.ai

Settings → Connectors → Add custom connector, then paste:
https://api.zerowidth.ai/mcp/x/caliper

Cursor · .cursor/mcp.json in a project, or ~/.cursor/mcp.json

{
  "mcpServers": {
    "caliper": {
      "url": "https://api.zerowidth.ai/mcp/x/caliper"
    }
  }
}

VS Code · .vscode/mcp.json

{
  "servers": {
    "caliper": {
      "type": "http",
      "url": "https://api.zerowidth.ai/mcp/x/caliper"
    }
  }
}

VS Code (command line) · Bash or zsh terminal (macOS, Linux)

code --add-mcp '{"name":"caliper","type":"http","url":"https://api.zerowidth.ai/mcp/x/caliper"}'

Claude Code

claude mcp add --transport http caliper https://api.zerowidth.ai/mcp/x/caliper

Try it in the MCP Inspector · runs on your machine, opens in your browser · Node 22.19+

npx @modelcontextprotocol/inspector@2.11.0 --server-url https://api.zerowidth.ai/mcp/x/caliper --transport http

Optional settings the entry also lists (left out above): Authorization.
The server runs on the operator's infrastructure; it may ask you to sign in when you first connect.
The MCP Inspector lists the server's tools, resources and prompts; a tool you call there runs for real.

Built from the server's registry entry with each client's documented format (checked 2026-10-14; the Cursor link and the VS Code command 2026-10-19; the MCP Inspector command 2026-10-21). Values in < > are yours to fill in; this page never contains a key. Where the server needs a setting the entry does not declare, it can still fail to start.

Does the registry listing match what we found?

Feature #6

The registry verifies a package once, when it is published, and does not re-check it. A difference below is about the listing, not a judgement of the publisher.

Registry says	We found	Result	Source · date
Remote endpoint api.zerowidth.ai/mcp/x/caliper	Session opened	matches	our test · 2026-10-23
No credential declared as required	Opened a session without any credential	matches	our test · 2026-10-23

Choosing

Record checks

Public records · not a safety rating

1 of 2 record checks met · 7 do not apply

Not ranked by downloads: a remote server publishes no download figure
Not ranked by stars: no public GitHub repository

MetRegistry entry is active and says how to run itActive, with a package or a remote address.
Not metSource repository link opensThe registry entry gives no repository link.
Does not applyRepository is not archivedNo public GitHub repository to read.
Does not applyCode pushed to the repository in the 90 days before our checkNo public GitHub repository to read.
Does not applyRepository publishes a security policy (SECURITY.md)No public GitHub repository to read.
Does not applyPackage names its licence with a standard (SPDX) identifierRemote server: it ships no package.
Does not applyThe version the registry lists can be installed and is not withdrawnRemote server: it ships no package.
Does not applynpm package carries build provenance (attestation)Remote server: it ships no package.
Does not applyNo known critical or high advisory in the package or its dependenciesRemote server: it ships no package.

Read from public records only: the registry entry, npm/PyPI, GitHub and advisory databases, checked 2026-10-22. No tool was called. Only “met” and “not met” are counted, so the total differs between servers; a check that does not apply or that we could not run is listed, never counted against it. It is not a safety rating. How each check works · Leaderboards

Common questions about ai.zerowidth/caliper

Answered from the data above

Is ai.zerowidth/caliper safe to install?

We do not rate servers as safe or unsafe. 1 of its 2 applicable record checks are met (facts from public records, each listed on this page). What the records show: 20 of its tools describe changing data (our AI model's reading of the descriptions). These are facts with their sources on this page, not a safety guarantee, and we did not run its tools.

Is ai.zerowidth/caliper free to use?

Its website (zerowidth.ai/docs/overview/account/plans-and-billing) describes a freemium pricing model. This is an AI-classified reading of the page on 2026-10-23, so check the page itself before relying on it.

Does ai.zerowidth/caliper need an API key or sign-in?

It opened a session without any credential on 2026-10-23. The registry entry declares no required credential; no declaration is not a guarantee.

Has ai.zerowidth/caliper been security tested?

Partly. 4 of the 15 checks that apply to it were exercised. It accepted a session without any credential and lists tools whose names suggest they change data. We did not call them. No security verdict is published before verification.

What can ai.zerowidth/caliper do?

It lists 45 tools. In our AI model's reading of their descriptions (two runs had to agree, nobody checked it by hand), they include tools that read or search, create or change data, delete, run code or commands and generate content. We did not call any tool, so this describes the text, not the behaviour.

Can ai.zerowidth/caliper change or delete data?

20 of its tools say in their description that they create, edit, delete, send or run something (our AI model's reading). We did not call any tool, so we cannot say what actually happens.

Found this page useful?

Anonymous · no sign-in

A quick, anonymous reaction — no account, no email. One per kind from your browser. The tally updates when the page is next refreshed, and it is only a rough count, never a safety rating or a measured number of people.

Similar servers

Same topic · AI-read

io.github.michael-denyer/hot-memory-mcpalso has tools that creates or changes data, deletes, runs code or commands, generates content, reads or searchescompare with this one
io.github.YashvantHange/supermemorySuperMemoryalso has tools that creates or changes data, deletes, runs code or commands, generates content, reads or searchescompare with this one
io.github.Opita-Code/dark-memory-mcpdark-memory-mcpalso has tools that creates or changes data, deletes, runs code or commands, generates content, reads or searchescompare with this one
ai.entityenricher/enricherEntity Enricheralso has tools that creates or changes data, deletes, runs code or commands, generates content, reads or searchescompare with this one
io.github.ExpertVagabond/watsonxalso has tools that creates or changes data, deletes, runs code or commands, generates content, reads or searchescompare with this one
io.github.crunchtools/geminiMCP Geminialso has tools that creates or changes data, deletes, runs code or commands, generates content, reads or searchescompare with this one

Active servers whose topic is also “ai-and-ml” and that have at least one tool of the same kind; most kinds in common first, then most GitHub stars. The topic and the tool kinds are an AI model's reading of the publishers' descriptions, not checked by hand. Similar is not a recommendation.

Compare with another server

Side by side: registry entry, our read-only session, the tools and the 18 classification fields. Same values as each page; no score.

Security testing

What did we test, and what did we leave out?

18 checks · features #1, #2

Open without sign-in

It accepted a session without any credential and lists tools whose names suggest they change data. We did not call them. No security score is given; a check we did not run is never counted as passed.

The 18 checks at a glanceour test · 2026-10-23

Inventory: exercised
Hidden instructions: exercised
Real execution: not run · our policy
Secret leak: not run · nothing to check it against
Internal addresses: not run · our policy
Unconfirmed changes: not run · our policy
Bad input: not run · our policy
Model requests: not run · nothing to check it against
Sensitive questions: not run · nothing to check it against
Folder boundary: not run · our policy
Log leaks: not run · nothing to check it against
Hidden content: exercised
Fake assistant turns: not applicable
Token passthrough: not applicable
Token audience: not applicable
Sign-in redirect: not run · our policy
Consent handling: not testable from outside
Sign-in metadata: exercised

4 exercised11 not run (reason given)3 not applicable

Each check ends in exactly one state: exercised, not run (with the reason), or not applicable (with the reason). 4 of the 15 checks that apply to it were exercised. We do not publish security-check outcomes for named servers.

Exercised · 4

1Inventory
tool-listReads the declared tools, resources and prompts.exercised
2Hidden instructions
description-poisoningLooks for hidden instructions in tool descriptions.exercised
12Hidden content
audience-hidingChecks resources that hide content from the user.exercised
18Sign-in metadata
oauth-url-schemeChecks the published sign-in metadata for unsafe URLs.exercised

Not run, with the reason · 11

3Real execution
real-executionCalls a tool and checks what really happens.This check calls the server's tools. ProtocolProbe calls no server's tools for anything it publishes; an operator can run this check on their own server with our self-test command.not run · our policy
4Secret leak
canary-leakPlants a fake secret and checks whether it leaks.This check needs at least one successful tool call to have something to check, and no tool was called.not run · nothing to check it against
5Internal addresses
ssrfChecks whether a tool can be steered to internal addresses.This check calls the server's tools. ProtocolProbe calls no server's tools for anything it publishes; an operator can run this check on their own server with our self-test command.not run · our policy
6Unconfirmed changes
write-without-confirmationChecks whether tools that change data act without asking.This check calls the server's tools. ProtocolProbe calls no server's tools for anything it publishes; an operator can run this check on their own server with our self-test command.not run · our policy
7Bad input
error-handlingSends bad input and watches how the server answers.This check calls the server's tools. ProtocolProbe calls no server's tools for anything it publishes; an operator can run this check on their own server with our self-test command.not run · our policy
8Model requests
samplingChecks whether the server asks the client's model to act for it.This check needs at least one successful tool call to have something to check, and no tool was called.not run · nothing to check it against
9Sensitive questions
elicitation-sensitive-dataChecks whether the server asks users for sensitive data.This check needs at least one successful tool call to have something to check, and no tool was called.not run · nothing to check it against
10Folder boundary
root-boundaryChecks whether the server reaches outside the folders it was given.This check calls the server's tools. ProtocolProbe calls no server's tools for anything it publishes; an operator can run this check on their own server with our self-test command.not run · our policy
11Log leaks
logging-side-channelChecks whether log messages carry data they should not.This check needs at least one successful tool call to have something to check, and no tool was called.not run · nothing to check it against
16Sign-in redirect
open-redirectChecks the sign-in redirect for abuse.Testing the sign-in redirect means sending probes to the operator's sign-in service, which we do not do.not run · our policy
17Consent handling
confused-deputyChecks consent handling when one service acts for another.Depends on the operator's own consent screen, which differs per server and cannot be tested from outside.not testable from outside

Does not apply to this server · 3

13Fake assistant turns
fake-assistant-turnChecks prompts that pose as the assistant's own words.The server exposes no prompts.not applicable
14Token passthrough
token-passthroughChecks whether the server forwards a user's token to other services.The server opened a session without sign-in, so there is no token flow to check.not applicable
15Token audience
token-audience-validationChecks whether tokens meant for another service are accepted.The server opened a session without sign-in, so there is no token flow to check.not applicable

Source: our own test, 2026-10-23, mcp-runtime-engine@0.1.0. Which checks count and why follows our published scoring model.

What happened during the test?

Feature #8

The steps in order, as the test record holds them.

0 msStarted a read-only session with the server's remote endpoint
1,393 msConnected after 0 redirects. No credential was sent or needed.
Read the inventory: 45 tools, 134 resources, 0 prompts.
18,744 msFinished: 4 checks exercised.

Reference

How is it classified?

18 fields

One value per field, each with its source. Fields written by AI models are marked. A field with no value says why.

TopicAI-classified

ai-and-ml

AI-classified · 2026-10-23

Pricing modelAI-classified

freemium

read from zerowidth.ai/docs/overview/account/plans-and-billing · 2026-10-23

“There are four tiers — Free , Starter , Pro , and Enterprise .”

Programming language

does not apply

no existing GitHub repository (server declares no repository link, so there is nothing to fetch)

Hosting type

remote (hosted by the publisher)

registry · 2026-10-23

MCP capability

resources, tools

our test · 2026-10-23

Transport

streamable HTTP

registry · 2026-10-23

Required credentials

none declared

registry · no declaration is not a guarantee

Package registry

does not apply

remote-only server: no package is shipped, so there is no package registry

Freshness

0–30 days

registry updatedAt · 2026-10-23

Lifecycle status

active

registry · 2026-10-23

License class

does not apply

remote-only server: ships no package, so there is nothing to look up in a package registry

Integrity hash

does not apply

remote-only server: ships no package, so there is nothing to look up in a package registry

Signature / provenance

does not apply

remote-only server: ships no package, so there is nothing to look up in a package registry

Dependency advisories

does not apply

ships no package, so there are no dependencies to audit

Popularity

does not apply

remote-only server: ships no package, so there is nothing to look up in a package registry

Publisher signals

not stated

no readable GitHub owner to describe

Maintenance

does not apply

server declares no repository link, so there is nothing to fetch

Environment

the publisher's infrastructure

where it runs, from the hosting type

“Not stated” means the source did not state it; “does not apply” means it does not apply to this kind of server; “our limit” means our own lookup failed. A linked value opens the directory filtered to the same value.

Cite or correct this page

Sources and corrections

Suggested citation

ProtocolProbe. “ai.zerowidth/caliper: MCP server record.” Data checked 2026-10-23. https://protocolprobe.com/mcp/servers/ai.zerowidth/caliper

Figures are valid for the date shown. Our facts on this page are CC BY 4.0: reuse them with a link and the check date. Quoted text (the publisher’s descriptions, website quotes, tool names) is not ours to license.

As JSON: this record in the API · API documentation.

Badge for your README

[![ProtocolProbe](https://protocolprobe.com/api/v1/badge/ai.zerowidth/caliper)](https://protocolprobe.com/mcp/servers/ai.zerowidth/caliper)

It shows this server's record-check count: facts from public records, no tool called. It is not a security rating or a pass. It links here and updates after each data reload.

Something wrong, or is this yours?

If a fact here is wrong, tell us and we will re-check it. If you operate this server, you can run our checks on it yourself with the free self-test command; we call no server’s tools ourselves for anything shown here.

Write to hello@protocolprobe.com · corrections log · methodology