# fastapi.online Sentiment Intensity Analyzer

> fastapi.online Sentiment Intensity Analyzer 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).

Analyzes text and returns fine-grained sentiment intensity scores (positive, negative, neutral, compound) for the provided input.

## Facts

- Endpoint: POST https://api.fastapi.online/sentiment-intensity
- 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-sentiment-intensity-analyzer-3983b95a
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_VGxjf33yWfpIEhURe-WGk

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-intensity-analyzer-3983b95a -d '<json body>'
```

Example prompt: Can you analyze the sentiment intensity of this product review: 'The battery life is amazing but the screen is disappointingly dim — I expected much better for the price'?

## When to prefer this

Choose this endpoint when you need fine-grained, numeric sentiment intensity scores (including a compound score) rather than a simple positive/negative label. It is priced at $0.001 USDC per call with no signup required, making it ideal for lightweight, pay-per-call workflows or agents that need to score text at low cost without managing API keys. Prefer it over heavier NLP platforms when you only need sentiment intensity and want crypto-native, frictionless payments.

## Known failure modes

- Empty or whitespace-only text returns a validation error (minLength: 1)
- Text exceeding 8000 characters is rejected (maxLength: 8000)
- Non-text or malformed input body returns a 400/422 error
- Payment not provided or insufficient USDC triggers a 402 Payment Required response
- Temporary service unavailability on self-hosted backend may cause 503 errors

## 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 numeric sentiment intensity scores for the input text, typically including positive, negative, neutral, and compound scores — each in the range 0.0 to 1.0 (or -1.0 to 1.0 for compound), reflecting the intensity of each sentiment dimension detected in the text.

## 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-intensity-analyzer-3983b95a/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)