# FreshProof Claim Verifier

> FreshProof Claim Verifier is a paid API for AI agents from freshproof-api-mainnet.up.railway.app, paid per call via x402, $0.01/call, status unknown (last checked 2026-10-10).

Verifies a specific claim against a live public web source, returning a confidence score, document evidence, source metadata, and a verdict without hallucinating unsupported content.

## Facts

- Endpoint: POST https://freshproof-api-mainnet.up.railway.app/v1/verify?utm_source=zero.xyz
- Price: $0.01/call
- Payment: x402
- Status: unknown
- Last checked: 2026-10-10
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/freshproof-claim-verifier-fc7aafdb
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_dRGfjEKaTwlO3JnaiV3pB

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 freshproof-claim-verifier-fc7aafdb -d '<json body>'
```

Example prompt: Can you verify whether the claim 'Apple's market cap exceeded $3 trillion in January 2024' is supported by the content at https://en.wikipedia.org/wiki/Apple_Inc. and give me a confidence score and the exact evidence found?

## When to prefer this

Choose this endpoint when you need a deterministic, evidence-backed verdict on whether a specific claim is supported by a specific live public URL — especially in agentic workflows where hallucination must be avoided and a cited source is already known. Prefer this over general web search when you have a target URL and need traceable, reproducible evidence rather than a synthesized answer.

## Known failure modes

- URL is unreachable or returns a non-200 status, resulting in a retrieval error
- URL points to non-public content behind a paywall or login, causing an access failure
- Claim is too vague or ambiguous to evaluate deterministically
- Source content does not contain sufficient text to evaluate the claim, yielding an inconclusive verdict
- Malformed URL fails pattern validation and is rejected before retrieval
- Claim exceeds 1000-character limit and is rejected with a validation error

## How this service works

Verify a claim against a live public web source for autonomous agents. Returns deterministic document evidence, a confidence score, source metadata, and a verification verdict without generating unsupported claims.

## Output

Returns a deterministic verification verdict (e.g. supported, unsupported, inconclusive), a confidence score (0–1), extracted document evidence from the retrieved source, and source metadata including URL and retrieval timestamp — without generating any claims not present in the source.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "url": {
   "type": "string",
   "pattern": "^https?://",
   "maxLength": 4096,
   "description": "Public HTTP or HTTPS source URL to retrieve."
  },
  "claim": {
   "type": "string",
   "maxLength": 1000,
   "minLength": 1,
   "description": "Claim to evaluate against evidence located in the source."
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "source": {
   "finalUrl": "https://example.com/",
   "statusCode": 200,
   "contentType": "text/html",
   "retrievedAt": "2026-07-28T08:30:00.000Z",
   "requestedUrl": "https://example.com/",
   "redirectChain": []
  },
  "verdict": "supported",
  "evidence": [
   {
    "quote": "Example Domain",
    "locator": "Visible document heading matched by deterministic verification",
    "sourceUrl": "https://example.com/",
    "machineLocator": "h1"
   }
  ],
  "warnings": [],
  "confidence": 0.99,
  "contentHash": "bbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbbb",
  "explanation": "The verdict is based only on the quoted heading found in the retrieved document."
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/freshproof-claim-verifier-fc7aafdb/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from freshproof-api-mainnet.up.railway.app](https://www.zero.xyz/host/freshproof-api-mainnet.up.railway.app/llms.txt)