VerifyAPI MCP Server

verify_claim

Fact-check a single factual claim against live web sources to receive a verdict with source details, confidence, and a signed verification receipt.

Instructions

Fact-check a single factual claim against live web sources. Returns one of supported, refuted, insufficient_evidence, or out_of_scope, with confidence, source_url, published_date, and a verbatim exact_quote from that source. Every response is signed with an Ed25519 receipt (verifiable at https://api.verify-api.dev/.well-known/jwks.json).

Pricing (see /v1/pricing): $0.02 base per supported/refuted verdict; recent tier (<24h old cache) 2x; fresh tier (cache bypassed, guaranteed live) 5x. insufficient_evidence, out_of_scope, malformed, and cache hits within your account are free. Use freshness="cached" (default) for maximum savings; freshness="fresh" when you need a guaranteed-current answer (breaking news, live standings, latest release); set max_age_seconds for HTTP Cache-Control-style bounded staleness.

Running without an API key uses the FREE TRIAL (3 calls per IP per 24h, cached tier only, still returns signed receipts). Set VERIFYAPI_API_KEY in the mcpServers env block to remove the limit and unlock the recent/fresh tiers. Get a key at https://verify-api.dev/signup (no credit card).

Use this before committing to any factual claim you are not sure about — dates, statistics, prices, attributions, event outcomes.

Input Schema

TableJSON Schema

Name	Required	Description
`as_of`	No	Optional ISO date (YYYY-MM-DD). Use for time-sensitive facts, e.g. prices or standings.
`claim`	Yes	A single factual claim, ideally under 300 characters. If you have multiple claims, call verify_claim once per claim.
`freshness`	No	Optional freshness tier. `fresh` bypasses both caches and runs the full pipeline (5x price) — use when you need a guaranteed-current answer (breaking news, live standings, latest release version). `cached` (default) honors both cache tiers. See GET /v1/pricing for exact multipliers. (Ignored in trial mode — trial is cached-only.)
`max_wait_ms`	No	Optional soft deadline in milliseconds. Default 15000. If the pipeline cannot finish in time you'll get insufficient_evidence.
`max_age_seconds`	No	Optional maximum age (in seconds) for a cached verdict. Acts like HTTP Cache-Control: max-age. Values below 3600 trigger the `fresh` tier; below 86400 trigger the `recent` tier (2x price). If both `freshness` and `max_age_seconds` are set, `freshness` wins. (Ignored in trial mode.)

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.9Sep 19, 2026

TDQS

A4.6/5.0

Behavior5/5

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

With no annotations provided, the description carries the full burden of behavioral disclosure, and it does so thoroughly. It explains return values, signed receipts, pricing tiers, cache semantics, trial limits, API key requirements, and the consequence of hitting max_wait_ms. No contradictions exist between description and annotations.

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?

The description is front-loaded with the core purpose and output shape before moving into pricing and trial details. It is longer than average, but the pricing, caching, and authentication information all support correct invocation and cost-aware decision-making.

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?

Given there is no output schema, the description fully explains the return fields and verdict values. It also covers authentication, rate limits, pricing, caching behavior, and when to use fresh vs cached mode, leaving no critical gap for an agent to invoke the tool correctly.

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 baseline is 3, but the description adds meaningful semantic value beyond the schema: it explains cost multipliers for freshness choices, trial-mode restrictions, and how max_age_seconds interacts with tiers. This helps an agent choose parameter values, not just parse them.

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?

The description names a specific verb and resource: fact-check a single factual claim against live web sources. It also enumerates the exact verdict values returned, which makes the tool's purpose unmistakable even without siblings to differentiate from.

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?

The description gives explicit guidance: use it before committing to uncertain factual claims, and choose freshness tiers based on whether a current answer is needed. It does not state explicit exclusions or compare against alternative tools, but with no siblings and clear contextual triggers, this is strong usage guidance.

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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