# fastapi.online — Error Explain

> fastapi.online — Error Explain is a paid API for AI agents from api.fastapi.online, paid per call via x402, $0.001/call, status down (last checked 2026-09-15).

Analyzes an error message or stack trace and returns a plain-language explanation with likely causes and suggested fixes

## Facts

- Endpoint: POST https://api.fastapi.online/error-explain
- Price: $0.001/call
- Payment: x402
- Status: down
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/fastapi-online-error-explain-ed2eacae
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_6RK9md7o9yNZ23XLJbzi0

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 fastapi-online-error-explain-ed2eacae -d '<json body>'
```

Example prompt: Can you explain what this error means and how to fix it: 'TypeError: Cannot read properties of undefined (reading map) at App.js:42'?

## When to prefer this

Choose this endpoint when you need a quick, cheap ($0.001 USDC), no-signup AI-powered explanation of any error message, stack trace, or exception — especially useful in automated CI/CD pipelines, developer bots, or coding assistants that need on-demand error diagnosis without sending data to a large third-party LLM provider.

## Known failure modes

- Empty or whitespace-only error_text returns validation error
- error_text exceeding 20,000 characters is rejected
- Vague or incomplete error snippets may yield generic or low-confidence explanations
- Payment not included or insufficient USDC triggers 402 response

## How this service works

Chat, embeddings, OCR, speech-to-text, image editing, image understanding (captioning/Q&amp;A), text-to-speech, translation, writing tools, classification tools, developer tools, local utilities, format/checksum validators, encoding &amp; crypto utilities, date/time calculators, geo/coordinate math, math &amp; finance calculators, novelty tools, and business/social writing generators — 179 endpoints in all, across multiple specialized self-hosted models. Pay per call with crypto — no signup — or get an API key.

## Output

A plain-language explanation of the error including what the error means, its likely root cause, and actionable suggestions for resolving it, generated by a self-hosted AI model.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "error_text": {
   "type": "string",
   "maxLength": 20000,
   "minLength": 1
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fastapi-online-error-explain-ed2eacae/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.fastapi.online](https://www.zero.xyz/host/api.fastapi.online/llms.txt)