ProofMart

Verify a factual claim

verify_claim

Submit one factual claim to ProofMart and get back a verdict (TRUE / FALSE / MIXED / UNVERIFIED), a confidence score (0-100), the evidence behind the verdict, and a signed receipt. Verdicts are remembered in ProofMart's Ledger: a claim that was already checked and is still fresh is answered instantly from memory (the result's 'source' field says 'ledger'; fresh research says 'checker'). Compound claims are split into individual facts automatically. One call = one metered check against the customer's plan.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "claim": "<claim>"
    },
    "name": "verify_claim"
  }
}

Input Schema

Name	Required	Description	Default
`claim`	Yes	The factual claim to verify, e.g. 'The Eiffel Tower is in Paris.'

Output Schema

Name	Required	Description	Default
`claim`	Yes
`source`	No
`account`	No
`receipt`	No
`verdict`	Yes
`evidence`	No
`confidence`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedOct 25, 2026

TDQS

A4.7/5.0

Behavior5/5

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

Goes well beyond the annotations by disclosing the result shapes ('source' = ledger vs checker), automatic compound-claim splitting, receipt signing, and per-call billing. These details are consistent with readOnlyHint=false, idempotentHint=false, and openWorldHint=true — a non-idempotent, externally-billed call is exactly what the metering sentence describes.

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

Conciseness5/5

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

Front-loaded with the action and the return shape, then layered with cache, splitting, and billing details in descending priority. No sentence is redundant or restates the title.

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?

Despite having an output schema, the description still covers verdict vocabulary, confidence range, and the 'source' field, plus cost and caching semantics — everything an agent needs to decide whether to call and how to interpret the response.

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

Parameters4/5

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

Schema coverage is 100%, so the `claim` parameter's format is already documented; the description adds real meaning by noting that a single `claim` value may contain a compound statement that gets split into individual facts. That is a usage-relevant behavior of the parameter not captured in the schema.

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 and resource ('Submit one factual claim to ProofMart') and immediately enumerates the exact return payload (verdict enum, confidence 0-100, evidence, signed receipt). It is clearly distinguishable from the only sibling, list_plans, without opening either schema.

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

Usage Guidelines4/5

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

Gives strong contextual guidance: it discloses the metered cost model ('One call = one metered check') and explains the ledger-cache path so an agent knows a repeat check may be free and instant. It does not state explicit when-not-to-use conditions or name a sibling alternative, so it falls short of a 5.

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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