# fastapi.online Topic Extractor

> fastapi.online Topic Extractor is a paid API for AI agents from api.fastapi.online, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-14).

Extracts the main topics or themes from a block of text using self-hosted AI inference

## Facts

- Endpoint: POST https://api.fastapi.online/topic-extract
- Price: $0.001/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-14
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/fastapi-online-topic-extractor-4a752b97
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_KK5buw_hLDNSRgD41uGwJ

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-topic-extractor-4a752b97 -d '<json body>'
```

Example prompt: Can you extract the main topics from this article? Here's the text: 'The Federal Reserve raised interest rates again this week, citing persistent inflation in housing and energy markets. Economists are divided on whether further hikes will tip the economy into recession.'

## When to prefer this

Choose this endpoint when you need a cheap, no-signup, pay-per-call topic extraction call at $0.001 USDC, especially in automated pipelines where cost per call matters. Prefer it over heavyweight NLP APIs when you don't need entity linking or deep ontology mapping — just the main topics from a chunk of text up to 8000 characters.

## Known failure modes

- Text too short or empty — returns validation error or empty topic list
- Text exceeds 8000 character limit — rejected with input validation error
- Payment not provided — returns HTTP 402 Payment Required
- Ambiguous or incoherent text — may return low-quality or generic topics
- Service unavailable — returns 5xx error if self-hosted model is down

## 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 list of extracted topics or themes identified in the input text, typically as a set of labels or keyword phrases representing the primary subjects covered in the content.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "text": {
   "type": "string",
   "maxLength": 8000,
   "minLength": 1
  }
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/fastapi-online-topic-extractor-4a752b97/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)