# fastapi.online — API Error Message Improver

> fastapi.online — API Error Message Improver 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).

Takes a raw API or software error message and returns a clearer, more actionable, human-readable version of it

## Facts

- Endpoint: POST https://api.fastapi.online/api-error-message-improve
- 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-api-error-message-improver-b54a64ac
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_0p4K40tozsssRf8tjLUEr

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-api-error-message-improver-b54a64ac -d '<json body>'
```

Example prompt: Can you improve this error message so it's clearer and more actionable for developers: 'NullPointerException at com.example.service.UserService.getUser(UserService.java:42)'?

## When to prefer this

Choose this endpoint when you need a quick, cheap ($0.001 USDC), no-signup solution for transforming cryptic or verbose error messages into clear, user-friendly text. Ideal for developer tools, API wrappers, or applications that want to surface better error UX without building a custom LLM pipeline. Prefer over general-purpose LLMs when you want a pay-per-call, no-account-required approach via crypto payment.

## Known failure modes

- Empty or whitespace-only error_message returns a validation error
- Error messages exceeding 2000 characters are rejected
- Highly domain-specific or proprietary error codes may not be improved meaningfully
- Payment failure or 402 status if no valid crypto payment or API key is provided

## 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 rewritten, improved version of the submitted error message — clearer, more human-readable, and ideally more actionable, helping developers or end users understand what went wrong and what to do about it.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "error_message": {
   "type": "string",
   "maxLength": 2000,
   "minLength": 1
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fastapi-online-api-error-message-improver-b54a64ac/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)