# VERITY Conversational Fact-Checker

> VERITY Conversational Fact-Checker is a paid API for AI agents from verity.basechainlabs.com, paid per call via x402, $0.1/call, status unknown (last checked 2026-09-14).

Checks a claim's factual status and returns a verdict (CURRENT/OUTDATED/DISPUTED/UNVERIFIABLE) with confidence score and sources, with persistent memory to skip re-checking previously verified claims across sessions.

## Facts

- Endpoint: POST https://verity.basechainlabs.com/api/agent
- Price: $0.1/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/verity-basechainlabs-com-19b5de05
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_xcGtPxOobNV701DCdCB18

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 verity-basechainlabs-com-19b5de05 -d '<json body>'
```

Example prompt: Can you fact-check this claim for me: 'The global average temperature has risen by 1.5°C since pre-industrial times' — I need to know if it's current, outdated, or disputed, along with your confidence level and the sources you used?

## When to prefer this

Choose VERITY when your agent needs structured fact-checking verdicts with source citations and must avoid redundant API calls across multi-session workflows. The persistent memory feature is especially valuable for agents that repeatedly check overlapping claims. Prefer over generic search when you need a structured CURRENT/OUTDATED/DISPUTED/UNVERIFIABLE verdict with confidence scores rather than raw search results.

## Known failure modes

- Claim is too vague or ambiguous to verify — returns UNVERIFIABLE with low confidence
- Claim references very recent events not yet indexed — may return UNVERIFIABLE or stale sources
- Payment not received or insufficient USDC — request rejected
- Network timeout or service unavailable — HTTP 5xx
- Claim previously checked returns stale cached result if underlying facts have changed since last session check

## How this service works

Conversational fact-checking with persistent memory — VERITY remembers what your agent has checked across sessions, skipping repeat lookups. Returns CURRENT/OUTDATED/DISPUTED/UNVERIFIABLE verdicts with confidence scores and sources. 0.10 USDC/call.

## Output

Returns one of four verdicts — CURRENT, OUTDATED, DISPUTED, or UNVERIFIABLE — along with a confidence score (0–1), cited sources, and a summary of what has changed if the claim is outdated. If this claim was previously checked in a prior session, returns the cached result immediately to save tokens.

## Example request

```json
{
 "claim": "Water boils at 100 degrees Celsius at sea level",
 "context": "Physics and chemistry fact",
 "priority": "standard"
}
```

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "$schema": "https://json-schema.org/draft/2020-12/schema",
 "required": [
  "input"
 ],
 "properties": {
  "input": {
   "type": "object",
   "required": [
    "type",
    "method",
    "bodyType",
    "body"
   ],
   "properties": {
    "body": {
     "required": [
      "query"
     ],
     "properties": {
      "query": {
       "type": "string",
       "description": "Claim, URL, or question to verify. E.g. 'Is X still true?', 'Check this URL: https://...'."
      },
      "caller_id": {
       "type": "string",
       "description": "Optional stable ID for persistent memory across verification sessions."
      }
     }
    },
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "POST",
      "PUT",
      "PATCH"
     ],
     "type": "string"
    },
    "bodyType": {
     "enum": [
      "json",
      "form-data",
      "text"
     ],
     "type": "string"
    }
   },
   "additionalProperties": false
  },
  "output": {
   "type": "object",
   "required": [
    "type"
   ],
   "properties": {
    "type": {
     "type": "string"
    },
    "example": {
     "type": "object",
     "properties": {
      "status": {
       "type": "string"
      },
      "tokens": {
       "type": "number"
      },
      "artifact": {
       "type": "object"
      }
     }
    }
   }
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/verity-basechainlabs-com-19b5de05/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from verity.basechainlabs.com](https://www.zero.xyz/host/verity.basechainlabs.com/llms.txt)