# GET /docs/lib: $0.005 per call

Up-to-date docs for any npm, PyPI, crates or Go library, trimmed for a coding agent's context: finds the project's own llms.txt and docs pages (or the latest release's README), keeps the sections relevant to your topic, within a token budget, with sources and the current version. Stops agents using stale APIs. ?library=hono&topic=middleware&tokens=3000

- **Price:** $0.005 in USDC, the same on Base, Solana, Polygon, Arbitrum. Failed calls are never charged.
- **Free trial:** yes, 20 free calls a day from Claude, Cursor or any MCP client ([set-up](/mcp/setup)).
- **Tier:** cached
- **Answers cached for:** 6 hour(s)
- **Data sources:** Project llms.txt and docs pages (free); npm/PyPI/crates.io/Go proxy metadata (free); jsDelivr and GitHub READMEs (free)
- **Lane:** AI coding agents ([OpenAPI](/openapi/coding.json))
- **Live health:** [status page](/status)

## Free sample

See an answer for the demo input first, free (no payment, 10 a minute): [https://aayatai.com/sample/docs-lib](/sample/docs-lib). It is a stored real answer when we have one, otherwise an example marked `"kind": "illustrative"`.

```bash
curl "https://aayatai.com/sample/docs-lib"
```

## 1. See the price (free)

Call it without paying: you get `402 Payment Required` and a `PAYMENT-REQUIRED` header with the exact price and where to pay.

```bash
curl -i "https://aayatai.com/docs/lib?library=hono&ecosystem=npm&topic=cors+middleware&tokens=3000"
```

## 2. Pay and call (TypeScript)

```bash
npm install @x402/fetch @x402/evm viem
```

```ts
import { wrapFetchWithPaymentFromConfig } from "@x402/fetch";
import { ExactEvmScheme } from "@x402/evm";
import { privateKeyToAccount } from "viem/accounts";

// A wallet used only by your agent, holding a little USDC on Base.
const account = privateKeyToAccount(process.env.WALLET_PRIVATE_KEY as `0x${string}`);
const pay = wrapFetchWithPaymentFromConfig(fetch, {
  schemes: [{ network: "eip155:8453", client: new ExactEvmScheme(account) }],
});

const res = await pay("https://aayatai.com/docs/lib?library=hono&ecosystem=npm&topic=cors+middleware&tokens=3000");
console.log(await res.json());
```

## 3. Or as an MCP tool

```ts
// MCP server: https://aayatai.com/mcp (Streamable HTTP). With the x402 MCP client (see /start):
const result = await client.callTool("docs-lib", {"library":"hono","ecosystem":"npm","topic":"cors middleware","tokens":3000});
```

## Inputs

- `library` **(required)** (string): Library/package name as published, e.g. hono, fastapi, serde, github.com/gin-gonic/gin.
- `ecosystem` (string; one of `npm`, `pypi`, `crates`, `go`; default `npm`): Package ecosystem: npm, pypi, crates (Rust) or go (Go modules).
- `topic` (string): What you need, e.g. routing, authentication, streaming responses (default: overview).
- `tokens` (integer; default `4000`): Most tokens of documentation to return.

Bad inputs are rejected with HTTP 400 before any payment is asked for.

## Example answer

```json
{
  "library": "hono",
  "ecosystem": "npm",
  "version": "4.13.9",
  "topic": "cors middleware",
  "content": "<!-- source: https://hono.dev/docs/middleware/builtin/cors -->\n# CORS Middleware\n\n```ts\nimport { cors } from 'hono/cors'\napp.use('/api/*', cors())\n```",
  "tokens": 42,
  "truncated": false,
  "sources": [
    {
      "url": "https://hono.dev/docs/middleware/builtin/cors",
      "kind": "docs-page"
    }
  ],
  "homepage": "https://hono.dev",
  "fetchedAt": "2026-09-28T12:00:00.000Z"
}
```

## Related

- [GET /docs/find](/services/docs-find) ($0.003): Find the AI-ready docs for any library or API: checks the project's docs site (from its npm, PyPI, crates or Go metadata) or any company domain (docs., develope
- [POST /docs/answer](/services/docs-answer) ($0.02): Ask a coding question about any npm, PyPI, crates or Go library and get an answer written only from its current docs (project llms.txt, docs pages or latest REA
- [GET /openapi](/services/openapi) ($0.005): Understand any public API fast: give its OpenAPI/Swagger spec URL, its docs or base URL, or a name from the APIs.guru directory (?api=stripe.com); we find the s
- [GET /library/research](/services/library-research) ($0.10): Premium research report on a library or API for coding agents: reads its current docs for your goal, checks version, safety and repository health, gathers what 
- [GET /package/check](/services/package-check) ($0.005): Should a coding agent install this package?
- [GET /dependency/verdict](/services/dependency-verdict) ($0.03): "Should I use this dependency?" in one call for npm, PyPI, crates or Go: full package safety check (vulnerabilities, malware, typosquats, deprecation, licence, 
- [GET /dependency/report](/services/dependency-report) ($0.08): Premium "should I use this dependency?" report: package safety (vulnerabilities, malware, typosquats, deprecation), GitHub repository health, licence compatibil
- [GET /package/changes](/services/package-changes) ($0.005): What changed between two versions of an npm, PyPI, crates or Go package: every release's notes from GitHub releases (or the CHANGELOG), newest first, with lines

New here? [Getting started in 60 seconds](/start). All services: [Aayat AI](/).