Readability

Flesch Reading Ease score and Flesch–Kincaid grade level for English text, plus word/sentence/syllable counts.

Input

Field	Type	Description
text *	string

Example output

{
  "readingEase": 100,
  "gradeLevel": 0.5,
  "words": 9,
  "sentences": 2
}

Try it - see the 402 challenge (free)

curl -i -X POST https://agent402.tools/api/readability \
  -H "Content-Type: application/json" \
  -d '{"text":"The cat sat on the mat. It was warm."}'

The response is HTTP 402 Payment Required with exact payment requirements. Any x402 v2 client pays automatically and retries:

Paid call (JavaScript agent)

import { wrapFetchWithPayment } from "@x402/fetch";
import { x402Client } from "@x402/core/client";
import { registerExactEvmScheme } from "@x402/evm/exact/client";
import { privateKeyToAccount } from "viem/accounts";

const client = new x402Client();
registerExactEvmScheme(client, { signer: privateKeyToAccount(KEY) });
const payFetch = wrapFetchWithPayment(fetch, client);

const res = await payFetch("https://agent402.tools/api/readability", {
  method: "POST",
  headers: { "Content-Type": "application/json" },
  body: JSON.stringify({
    "text": "The cat sat on the mat. It was warm."
  }),
});

No wallet? Pay with compute

This is a pure-CPU tool, so an agent without a wallet can pay with proof-of-work instead of USDC: fetch a challenge, solve the sha256 puzzle (16 leading zero bits - a fraction of a second of CPU, no money, no AI tokens), and resend with the X-Pow-Solution header.

import { createHash } from "node:crypto";
const lz = (b) => { let t = 0; for (const x of b) { if (!x) { t += 8; continue; } t += Math.clz32(x) - 24; break; } return t; };
const c = await (await fetch("https://agent402.tools/api/pow/challenge?slug=readability")).json();
let n = 0;
while (lz(createHash("sha256").update(c.challenge + ":" + n).digest()) < c.difficulty) n++;
await fetch("https://agent402.tools/api/readability", { method: "POST", headers: { "X-Pow-Solution": c.token + ":" + n, "Content-Type": "application/json" }, body: JSON.stringify({"text":"The cat sat on the mat. It was warm."}) });

Part of these workflows

This tool is one step in 2 curated multi-tool workflows - agents can fetch the whole sequence as an MCP prompt or call https://agent402.tools/api/skill-packs/{slug}/prompt.

• Text hygiene - Turn a wall of dirty text - chat logs, scraped pages, user-generated content, log dumps - into something safe to store, search, and pipe into the next step. Measure first, redact PII before anything else touches the data, then dedupe, sort, extract entities, surface keywords, and grade the readability of what's left.
• WCAG accessibility audit - Run a deterministic WCAG 2.x audit of an HTML page from a string and a fg/bg color pair. Checks language attribute (3.1.1), document title (2.4.2), heading order (1.3.1), link-text presence (2.4.4), color contrast (1.4.3), and reading grade level (3.1.5 AAA). Seven pure-CPU tools, no headless browser needed - the canonical accessibility-first-pass workflow done as a single round-trip of tool calls.

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