# POST /compat/check: $0.005 per call

Do these package versions work together and on your runtime? Give up to 20 npm or PyPI packages (exact versions, ranges or latest) plus your Node or Python version; each package's engines, peer dependencies or Requires-Python / Requires-Dist are checked against the others and the runtime, with conflicts explained and end-of-life runtimes flagged.

- **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:** live
- **Answers cached for:** 6 hour(s)
- **Data sources:** npm registry and PyPI metadata (free); deps.dev version lists (free); endoflife.date (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/compat-check](/sample/compat-check). It is a stored real answer when we have one, otherwise an example marked `"kind": "illustrative"`.

```bash
curl "https://aayatai.com/sample/compat-check"
```

## 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 -X POST https://aayatai.com/compat/check -H "content-type: application/json" -d '{"packages":["react-router@7.1.0","react@18.3.1","react-dom@18.3.1"],"node":"18.20.0"}'
```

## 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/compat/check", {
  method: "POST",
  headers: { "content-type": "application/json" },
  body: JSON.stringify({"packages":["react-router@7.1.0","react@18.3.1","react-dom@18.3.1"],"node":"18.20.0"}),
});
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("compat-check", {"packages":["react-router@7.1.0","react@18.3.1","react-dom@18.3.1"],"node":"18.20.0"});
```

## Inputs

- `packages` **(required)** (array): e.g. ["react-router@7.1.0", "react@18", "react-dom@18"] or ["fastapi==0.110.0", "pydantic==2.6.0"].
- `ecosystem` (string; one of `npm`, `pypi`; default `npm`): Default ecosystem for entries without an npm:/pypi: prefix.
- `node` (string): Your Node.js version, e.g. 18.20.0 or 20.
- `python` (string): Your Python version, e.g. 3.9 or 3.12.1.

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

## Example answer

```json
{
  "verdict": "incompatible",
  "packages": [
    {
      "ecosystem": "npm",
      "name": "react-router",
      "requested": "7.1.0",
      "version": "7.1.0",
      "runtime": ">=20.0.0"
    }
  ],
  "runtime": {
    "node": "18.20.0",
    "python": null,
    "eol": {
      "node": {
        "cycle": "18",
        "eol": "2025-04-30",
        "endOfLife": true,
        "latestInCycle": "18.20.8"
      }
    }
  },
  "constraints": [
    {
      "from": "react-router@7.1.0",
      "on": "node",
      "range": ">=20.0.0",
      "against": "18.20.0",
      "status": "conflict"
    }
  ],
  "conflicts": 1,
  "notChecked": 0,
  "advice": [
    "react-router@7.1.0 needs node >=20.0.0 but you have 18.20.0."
  ],
  "checkedAt": "2026-09-28T12:00:00.000Z"
}
```

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- [GET /docs/lib](/services/docs-lib) ($0.005): 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 re
- [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

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