# fastapi.online Sentiment Analysis

> fastapi.online Sentiment Analysis is a paid API for AI agents from api.fastapi.online, paid per call via x402, $0.001/call, status down (last checked 2026-09-16).

Classifies input text as positive, negative, or neutral sentiment for $0.001 USDC per call with no signup required

## Facts

- Endpoint: POST https://api.fastapi.online/sentiment
- Price: $0.001/call
- Payment: x402
- Status: down
- Last checked: 2026-09-16
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/fastapi-online-sentiment-analysis-a8c3cc36
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_5LUX4XKcVHy-zf7DJQLcA

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-sentiment-analysis-a8c3cc36 -d '<json body>'
```

Example prompt: Can you analyze the sentiment of this customer review and tell me whether it's positive, negative, or neutral: 'The delivery was super fast but the packaging was completely crushed when it arrived.'

## When to prefer this

Choose this endpoint when you need lightweight, pay-per-call sentiment classification without any account setup or subscription commitment. It is ideal for agents that process variable, unpredictable volumes of text and want crypto-native micropayment billing. Prefer this over heavier NLP platforms when you only need a simple positive/negative/neutral label and want minimal integration overhead.

## Known failure modes

- Missing 'text' field in request body returns a validation error
- Empty string input may return unexpected or unreliable sentiment
- Very long texts may hit token limits or produce degraded accuracy
- Payment failure (insufficient USDC balance) blocks the request with a 402 response
- Non-English text may return less accurate sentiment classification

## 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

Returns a JSON object with a 'sentiment' field containing one of three enum values: 'positive', 'negative', or 'neutral'. Additional fields may be present (additionalProperties: true), potentially including confidence scores or other metadata depending on the model response.

## 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-sentiment-analysis-a8c3cc36/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)