# The Stall — Fact Check (x402)

> The Stall — Fact Check (x402) is a paid API for AI agents from the-stall.intuitek.ai, paid per call via x402, $0.1/call, status unknown (last checked 2026-09-13).

Verifies a factual claim and returns a verdict (true/false/uncertain) with supporting reasoning, paid per-call in USDC via x402.

## Facts

- Endpoint: GET https://the-stall.intuitek.ai/cap/fact-check
- Price: $0.1/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-13
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/the-stall-fact-check-x402-9866fecd
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_yM87L8bE_236OV9mcbarl

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 the-stall-fact-check-x402-9866fecd
```

Example prompt: Can you fact-check this claim for me: 'The Eiffel Tower was built in 1889 as a permanent structure' — use the fact-check service and include any relevant historical context about its original purpose?

## When to prefer this

Use this endpoint when an AI agent needs to verify a discrete factual assertion without registering an account or obtaining an API key — particularly useful in automated pipelines where pay-per-call USDC billing (x402) is preferred over subscription models. Best for single, specific claims rather than broad research tasks.

## Known failure modes

- Vague or ambiguous claims may return uncertain verdicts rather than definitive true/false
- Payment failure or insufficient USDC balance blocks the request
- Claims requiring real-time or proprietary data may not be verifiable
- Extremely niche or obscure claims may return low-confidence results
- Missing required 'claim' query parameter returns a validation error

## How this service works

Domain-agnostic x402 capability chassis by IntuiTek¹. 300 AI-callable data services — pay USDC on Base mainnet. No accounts or API keys required.

## Output

A verdict on whether the submitted claim is true, false, or uncertain, along with a confidence signal and reasoning that supports the assessment.

## Example request

```json
{
 "input": {
  "type": "http",
  "method": "GET",
  "queryParams": {
   "claim": "The Earth orbits around the Sun",
   "context": "Basic astronomy and planetary motion"
  }
 }
}
```

## 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"
   ],
   "properties": {
    "type": {
     "type": "string",
     "const": "http"
    },
    "method": {
     "enum": [
      "GET"
     ],
     "type": "string"
    },
    "queryParams": {
     "type": "object",
     "required": [
      "claim"
     ],
     "properties": {
      "claim": {
       "type": "string",
       "description": "The factual statement to verify (e.g. 'The Eiffel Tower is 330 meters tall' or 'Apple was founded in 1976')."
      }
     },
     "additionalProperties": false
    }
   },
   "additionalProperties": false
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/the-stall-fact-check-x402-9866fecd/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from the-stall.intuitek.ai](https://www.zero.xyz/host/the-stall.intuitek.ai/llms.txt)