# fastapi.online — Exit Code Explainer

> fastapi.online — Exit Code Explainer is a paid API for AI agents from api.fastapi.online, paid per call via x402, $0.0005/call, status unknown (last checked 2026-09-15).

Explains what a given Unix/shell exit code means, optionally with execution context, using self-hosted AI inference.

## Facts

- Endpoint: POST https://api.fastapi.online/exit-code-explain
- Price: $0.0005/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/fastapi-online-exit-code-explainer-47dced49
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_FLx50czvm94dULoOVtWyh

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-exit-code-explainer-47dced49 -d '<json body>'
```

Example prompt: My script just failed with exit code 137 while running a Docker build — can you explain what that exit code means?

## When to prefer this

Choose this endpoint when an agent or developer needs a quick, cheap, on-demand human-readable explanation of a Unix/shell exit code, especially in automated pipelines, CI/CD workflows, or debugging tools. At $0.0005 per call with no signup required, it is ideal for pay-per-use agentic workflows. Prefer it over generic LLM chat endpoints when you want a dedicated, cost-predictable tool call with a structured input schema.

## Known failure modes

- Invalid or missing exit_code field returns a 422 validation error
- exit_code values outside typical range (0–255) may yield less precise explanations
- Context string exceeding 500 characters is rejected
- Payment not included or insufficient results in 402 Payment Required
- Model inference timeout on busy self-hosted infrastructure

## 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 human-readable explanation of what the given exit code means, including its conventional meaning in Unix/shell/Linux contexts, likely causes, and any signals it corresponds to. When context is provided, the explanation may be tailored to that execution environment.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "context": {
   "type": "string",
   "maxLength": 500
  },
  "exit_code": {
   "type": "integer"
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fastapi-online-exit-code-explainer-47dced49/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)