# fastapi.online — Readability Audience Analyzer

> fastapi.online — Readability Audience Analyzer is a paid API for AI agents from api.fastapi.online, paid per call via x402, $0.001/call, status unknown (last checked 2026-09-15).

Analyzes a block of text and returns its readability level and target audience profile

## Facts

- Endpoint: POST https://api.fastapi.online/readability-audience
- Price: $0.001/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-readability-audience-analyzer-c24e0102
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_8-b1yZ1Lc5eSkhO9BkeWA

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-readability-audience-analyzer-c24e0102 -d '<json body>'
```

Example prompt: Can you analyze this article intro and tell me what reading level it's written at and who the target audience seems to be? Here's the text: 'The mitochondria, often referred to as the powerhouse of the cell, orchestrate complex biochemical processes central to eukaryotic energy metabolism.'

## When to prefer this

Choose this endpoint when you need a quick, per-call readability and audience assessment without committing to a subscription-based writing platform. It is ideal for agents performing ad-hoc content quality checks, CMS workflows that need to gate or tag content by reading level, or educational tools that need to match material to student grade levels. Prefer this over general-purpose LLM prompting when you need a consistent, structured readability score rather than a freeform opinion.

## Known failure modes

- Empty or whitespace-only text returns a validation error
- Text exceeding 8000 characters is rejected
- Very short text (single words or fragments) may produce unreliable scores
- Non-English text may return inaccurate or irrelevant readability assessments
- Payment failure (402) if no valid x402 credentials are 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

Returns an assessment of the text's readability characteristics, including the estimated reading level, target audience profile, and difficulty classification, helping users determine whether their content matches their intended readers.

## 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-readability-audience-analyzer-c24e0102/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)