MCP Verification Gate: check an MCP server or an A2A agent before you connect or delegate

One glance: is this MCP server verified, with proof

is_verified

Read-onlyIdempotent

A single machine-first answer for an agent deciding whether to trust an MCP endpoint BEFORE it connects. Returns verified (true only when the latest scheduled measurement passed every measured condition; null otherwise, never false), a state enum saying which case it is, measured_at, and a record_sha256 with a recompute_url so you can check the verdict without trusting this gate. Reads the stored register only: it contacts nothing and measures nothing. Absent and pending are reported honestly and are NOT negative verdicts. For a fresh measurement rather than the stored one, use check_conformance.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`endpoint`	Yes	https URL of the MCP endpoint to look up, exactly as it appears on the register

Output Schema

TableJSON Schema

Name	Required	Description
`gate`	No	Name of this gate.
`state`	No	verified = passed all measured conditions. pending = measured but not passing every one (often only because determinism needs the owner's consent). held = could not be reached. watched = on the list, not yet measured. absent = no row here at all.
`reason`	No	One sentence saying why state has the value it has.
`endpoint`	No	The endpoint you asked about, echoed.
`verified`	No	true = latest measurement passed all measured conditions. null = not established here (see state). Never false: unmeasured or not-yet-passing is not a failure.
`conditions`	No	Per condition: true passed, false did not pass, null not measured. null as a whole when nothing was measured.
`record_url`	No	URL of the exact bytes that record_sha256 hashes, or null for a verdict stored before those bytes were kept.
`gate_commit`	No	Git commit of the deployed gate, or a sentence saying the deployment did not pin one.
`history_url`	No	URL of the stored measurements for this endpoint.
`measured_at`	No	Time of the latest stored measurement, or null when there is none.
`on_register`	No	true = the endpoint has a row here. false = the register was read and it has none.
`measurements`	No	Measured endpoints only: how many measurements are stored.
`how_to_appear`	No	Absent endpoint only: how anyone can add it to the register.
`recompute_url`	No	Where to fetch what record_sha256 can be checked against: record_url when it exists, otherwise the history.
`record_sha256`	No	Hash of the latest verdict. Recompute it via recompute_url; no trust in this gate required.
`recompute_note`	No	How to recompute record_sha256 from record_url, or why it cannot be recomputed.
`verified_meaning`	No	What verified true and null mean.
`absence_vs_failure`	No	Measured endpoints only: condition 06 from the latest measurement, disclosed and never a verdict.
`not_an_endorsement`	No	What a verified reading does not claim.

Schema Changelog

Changes observed during successful MCP inspections.

Changed16 schema fields changedOct 7, 2026

addedOutput schema / properties / absence_vs_failure

Added value: +{
+  "description": "Measured endpoints only: condition 06 from the latest measurement, disclosed and never a verdict.",
+  "type": [
+    "object",
+    "null"
+  ]
+}

addedOutput schema / properties / conditions / description

Added value: +"Per condition: true passed, false did not pass, null not measured. null as a whole when nothing was measured."

addedOutput schema / properties / endpoint / description

Added value: +"The endpoint you asked about, echoed."

addedOutput schema / properties / gate

Added value: +{
+  "description": "Name of this gate.",
+  "type": "string"
+}

addedOutput schema / properties / gate_commit

Added value: +{
+  "description": "Git commit of the deployed gate, or a sentence saying the deployment did not pin one.",
+  "type": "string"
+}

addedOutput schema / properties / history_url

Added value: +{
+  "description": "URL of the stored measurements for this endpoint.",
+  "type": "string"
+}

addedOutput schema / properties / how_to_appear

Added value: +{
+  "description": "Absent endpoint only: how anyone can add it to the register.",
+  "type": [
+    "string",
+    "null"
+  ]
+}

addedOutput schema / properties / measured_at / description

Added value: +"Time of the latest stored measurement, or null when there is none."

addedOutput schema / properties / measurements

Added value: +{
+  "description": "Measured endpoints only: how many measurements are stored.",
+  "type": "integer"
+}

addedOutput schema / properties / not_an_endorsement

Added value: +{
+  "description": "What a verified reading does not claim.",
+  "type": "string"
+}

addedOutput schema / properties / on_register / description

Added value: +"true = the endpoint has a row here. false = the register was read and it has none."

addedOutput schema / properties / reason

Added value: +{
+  "description": "One sentence saying why state has the value it has.",
+  "type": "string"
+}

addedOutput schema / properties / recompute_note

Added value: +{
+  "description": "How to recompute record_sha256 from record_url, or why it cannot be recomputed.",
+  "type": "string"
+}

addedOutput schema / properties / recompute_url / description

Added value: +"Where to fetch what record_sha256 can be checked against: record_url when it exists, otherwise the history."

addedOutput schema / properties / record_url

Added value: +{
+  "description": "URL of the exact bytes that record_sha256 hashes, or null for a verdict stored before those bytes were kept.",
+  "type": [
+    "string",
+    "null"
+  ]
+}

addedOutput schema / properties / verified_meaning

Added value: +{
+  "description": "What verified true and null mean.",
+  "type": "string"
+}

AddedAug 21, 2026

TDQS

A4.6/5.0

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnly/idempotent/non-destructive, but the description adds substantive behavior beyond them: it reads the stored register only and 'contacts nothing and measures nothing', explains that verified is null-not-false and that absent/pending are honest non-verdicts, and exposes a recompute_url for independent verification. That is rich, non-redundant disclosure.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loads the core value ('A single machine-first answer... BEFORE it connects') and every sentence carries distinct information (return contract, read-only scope, null semantics, alternative tool). Slightly dense but no wasted sentences.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Output schema exists so return-field explanation is not strictly required, yet the description voluntarily characterizes the return contract and edge cases (null vs false, pending). Combined with the schema and annotations, an agent has everything needed to call it correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Single parameter with 100% schema description coverage, so the schema already explains the endpoint format ('exactly as it appears on the register'). The description adds no further syntax or format detail beyond what the schema provides, so baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb+resource: returns a trust verdict ('verified', 'state enum', 'measured_at', 'record_sha256') for an MCP endpoint. It explicitly separates itself from check_conformance ('For a fresh measurement rather than the stored one'), so an agent can distinguish it from siblings without opening schemas.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives a clear when-to-use frame ('BEFORE it connects') and names the alternative for the contrasting case (check_conformance for fresh measurement). Exclusions are explicit, leaving nothing to inference.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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