# 24K Labs Readability Score API

> 24K Labs Readability Score API is a paid API for AI agents from api.24klabs.ai, paid per call via x402, $0.002/call, status unknown (last checked 2026-09-15).

Analyzes a text passage to return word/sentence/syllable counts, reading time, and six standard readability grade-level scores in a single call.

## Facts

- Endpoint: POST https://api.24klabs.ai/api/v1/readability-score
- Price: $0.002/call
- Payment: x402
- Status: unknown
- Last checked: 2026-09-15
- Activations on Zero: 0
- Tags: x402
- Canonical page: https://www.zero.xyz/c/24k-labs-readability-score-api-6e3d065a
- Structured record (JSON): https://api.zero.xyz/v1/capabilities/cap_EouOzsqWtvyVvjOZ6DRxV

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 24k-labs-readability-score-api-6e3d065a -d '<json body>'
```

Example prompt: Can you analyze the readability of this paragraph and give me all the grade-level scores — Flesch-Kincaid, Gunning Fog, SMOG, ARI, Coleman-Liau, and Flesch Reading Ease — plus the word count and estimated reading time? Here's the text: 'Effective communication requires clarity and precision. Overly complex language alienates readers and obscures meaning.'

## When to prefer this

Choose this endpoint when you need multiple readability metrics computed simultaneously in a single call, rather than calling separate services for each formula. It is ideal for content pipelines, editorial tools, accessibility audits, or educational applications that need to evaluate text complexity using industry-standard formulas (Flesch, Gunning Fog, SMOG, ARI, Coleman-Liau) alongside basic text statistics like word count and reading time. Prefer this over general-purpose LLM-based text analysis when you need deterministic, reproducible, numerically precise readability scores.

## Known failure modes

- Empty or missing text input returns a 400 validation error
- Extremely short text (1–2 words) may produce unreliable or undefined grade-level scores
- Non-English text may yield inaccurate readability scores as the formulas are designed for English
- Very large text payloads may time out or be rejected if they exceed request size limits
- Network or service unavailability returns a 5xx error

## How this service works

Word/sentence/syllable counts, reading time, plus Flesch Reading Ease, Flesch-Kincaid, Gunning Fog, SMOG, ARI, and Coleman-Liau grade levels in one call.

## Output

Returns a structured object containing word count, sentence count, syllable count, and estimated reading time, alongside six readability scores: Flesch Reading Ease (0–100 scale), Flesch-Kincaid Grade Level, Gunning Fog Index, SMOG Index, Automated Readability Index (ARI), and Coleman-Liau Index — all computed in a single API call.

## Request schema (JSON Schema)

```json
{
 "type": "object",
 "properties": {
  "text": {
   "type": "string"
  }
 }
}
```

## Response schema (JSON Schema)

```json
{
 "type": "json",
 "example": {
  "words": 17,
  "flesch_reading_ease": 90
 }
}
```

## More

- Live health (JSON, refreshed every minute): https://www.zero.xyz/c/24k-labs-readability-score-api-6e3d065a/health.json
- [Zero catalog index](https://www.zero.xyz/llms.txt)
- [Other services from api.24klabs.ai](https://www.zero.xyz/host/api.24klabs.ai/llms.txt)