# Agent Evidence API – Claim Verification

> Agent Evidence API – Claim Verification is a paid API for AI agents from agent-evidence.thx93.dev, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-22).

Verifies a claim or fact-checks a statement against up to 5 public web sources, returning cited evidence passages that support, contradict, or fail to settle the claim.

## Facts

- Endpoint: POST https://agent-evidence.thx93.dev/weather/mcp?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-22
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/agent-evidence-api-claim-verification-1982e1ea
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_QWUZ5ctVZRaAMiKpRSH2A

Status and success rate cover calls made through Zero and Zero's own probes. Third-party monitors may report differently.

## How to call it through Zero

Zero handles the 402 payment challenge and records the run. With the Zero CLI installed (`npm i -g @zeroxyz/cli`):

```sh
zero fetch --capability agent-evidence-api-claim-verification-1982e1ea -d '<json body>'
```

Example prompt: Can you fact-check the claim that 'The Eiffel Tower is 330 meters tall' against these two sources: https://www.toureiffel.paris/en/the-monument/key-figures and https://en.wikipedia.org/wiki/Eiffel_Tower — and show me the exact passages that support or contradict it?

## When to prefer this

Choose this endpoint when you need cited, auditable evidence from specific URLs to verify a claim — not just a web search. It is ideal when you have known source URLs and need exact passage excerpts with timestamps and content hashes for compliance, journalism, or research. Prefer it over generic search APIs when auditability and per-source attribution are required. The free 'sample' tool makes it safe to evaluate output quality before committing to paid calls.

## Known failure modes

- No content retrieved from provided URLs — no charge applied, empty result returned
- URL is inaccessible, paywalled, or returns a non-200 response — that source is skipped
- Claim is too ambiguous for the retrieved content to settle — passages returned as 'inconclusive'
- More than 5 URLs supplied — only up to 5 are processed
- Malformed MCP input schema or missing required 'toolName' field — validation error returned
- Rate limiting or payment failure via x402 — request rejected before processing

## How this service works

Verify a claim or fact check a statement against public web sources: send a question and up to 5 URLs, get cited evidence - passages that support, contradict or fail to settle it. Claim verification with a citation for every excerpt: source URL, retrieval time, content hash. Never charges when nothing is retrieved. Free to evaluate: the `sample` tool returns one real response at no cost, so you can judge the output before paying for your own question.

## Output

Returns a list of evidence passages from the provided URLs, each labeled as supporting, contradicting, or failing to settle the claim. Every excerpt includes the source URL it was retrieved from, the retrieval timestamp, and a content hash for auditability. No charge is incurred if no relevant content is retrieved.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "toolName",
    "inputSchema"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "mcp"
    },
    "method": {
     "type": "string"
    },
    "example": {
     "type": "object"
    },
    "toolName": {
     "type": "string"
    },
    "transport": {
     "enum": [
      "streamable-http"
     ],
     "type": "string"
    },
    "description": {
     "type": "string"
    },
    "inputSchema": {
     "type": "object"
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object"
    }
   }
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "result": [
   {
    "area": "Central Virginia",
    "event": "Winter Storm Warning",
    "severity": "Severe",
    "description": "Heavy snow expected.",
    "instructions": "Avoid travel."
   }
  ]
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/agent-evidence-api-claim-verification-1982e1ea/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from agent-evidence.thx93.dev](https://www.zero.xyz/host/agent-evidence.thx93.dev/llms.txt)