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x402lint

by something-agentversion 0.2.0i★ –iRuns in the cloud
Registry nameio.github.something-agent/x402lint

Install

Overview

Description from the maker (original English)

Free x402 endpoint linter: unpaid 402 challenge, payTo/asset/amount, CORS, directory readiness.

PopNx MCP’s three pillars

These three are never merged into one score: opinions, measurements and popularity are different things.

What you can do with it

We have not written a plain-language summary for this one yet. Below are the facts we read from the registry.

Install

Pick the AI app you use, then copy the settings.

Before you install

You need

Which app do you use?

Pick your app above. We remember it, so next time the button says “Install in …”.

Works in Claude on the web, desktop and mobile:

  1. Open Settings → Connectors
  2. Press Add custom connector
  3. Paste the address below and press Add
  4. If it asks you to sign in, sign in with the maker
SettingsConnectors1+ Add2https://…3
https://x402lint.something-agent.workers.dev/mcp

Run this in your terminal

claude mcp add --transport http x402lint https://x402lint.something-agent.workers.dev/mcp

Open in Cursor

Or copy the settings yourself

Paste into .cursor/mcp.json in your project, or ~/.cursor/mcp.json

{
  "mcpServers": {
    "x402lint": {
      "url": "https://x402lint.something-agent.workers.dev/mcp"
    }
  }
}

Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.

Open in VS Code

Or copy the settings yourself

Paste into .vscode/mcp.json in your project

{
  "servers": {
    "x402lint": {
      "type": "http",
      "url": "https://x402lint.something-agent.workers.dev/mcp"
    }
  }
}

Your browser asks to open the app, then the app shows the settings and asks you to confirm. Key values are left empty for you to fill in.

ChatGPT connects only to servers on the internet:

  1. Open ChatGPT on the web → Settings → Connectors (Apps)
  2. Press Create or Add (some plans need Developer mode under Advanced first)
  3. Paste the address below, give it a name and save
  4. If it asks you to sign in, sign in with the maker
SettingsConnectors1+ Create2https://…3
https://x402lint.something-agent.workers.dev/mcp

Menu names can differ slightly by plan and over time.

Your choice stays on this device in a cookie; no account needed.

These settings are generated from the maker’s registry entry. If the README says otherwise, follow the README.

What it can do

Tool names and descriptions exactly as the server reported them on Nov 7, 2026. The maker wrote them, not us; we show them as plain text.

  • lint_x402_endpoint

    Unpaid lint of an x402 endpoint: fetches the 402 (GET and POST), then checks the challenge (version, accepts[] fields, CAIP-2 network, payTo/asset/amount sanity, EIP-712 name/version, timeouts, resource), transport (redirects, cache headers, CORS) and discovery files. Returns fin

  • check_directory_readiness

    Lint an x402 endpoint's unpaid 402 and report, per directory, whether it meets what x402dash (unpaid GET must return 402), x402scan (OpenAPI x-payment-info or /.well-known/x402, input schema), the402 (validator 'payable') and the CDP/PayAI Bazaar (bazaar extension, description <=

  • lint_payment_required

    Lint a PaymentRequired object you already have (decoded JSON, a JSON string, or the raw base64 PAYMENT-REQUIRED header). Same field/value checks as lint_x402_endpoint, no network access. Free.

Basic checksi

We check information anyone can see; we have not read the code. Checks that do not apply are left out of the count. · Checked Nov 7, 2026

  • ✓ Pass

    Maker matches the repo

    The registry name was verified with the GitHub account something-agent, which owns the repo

  • … Not checked yet

    Still maintained

    We have not read this repo from GitHub yet

  • … Not checked yet

    Has a licence

    We have not read this repo from GitHub yet

  • ✓ Pass

    Endpoint responds

    Responded in 62 ms (HTTP 200)

  • – Not applicable

    Sign-in with OAuth

    No sign-in needed

  • ✓ Pass

    No hidden instructions in tool descriptions

    Read 3 tool descriptions and found no hidden instructions to the AI

Compared with others in Otheri

  • More stars than 0% of the other 32602 servers in this category
  • Published to the registry more recently than 78% of the other 32602 servers in this category
  • Basic checks equal to or better than 100% of the other 32602 servers in this category

Compared with every active server in this category in the registry. Stars count only when the publisher owns the repo.

Common questions

Is x402lint safe?

It passed 3 of 3 applicable basic checks. We have not read the code. Before adding a key or token, see what access the server asks for and use a key with only the permissions you need.

What keys or codes does it need?

The registry does not list a required key, though some servers ask you to sign in on first use.

Does it run on my computer or in the cloud?

It runs in the maker’s cloud. Connect over the internet with nothing to install, but what you send passes through the maker’s servers.

Is it still maintained?

The GitHub repo last changed –, and the latest version (0.2.0) reached the registry 10 days ago.

Which apps can use it?

Apps that support MCP, such as Claude Desktop, Claude Code, Cursor and VS Code. It connects by URL, so apps that accept remote MCP servers work too, such as ChatGPT in developer mode.

What can I use instead?

In the same category: Spec Driven Development, Remote Desktop Commander, Rystic

Alternatives

Servers in the same category from other makers, sorted by stars.

Reading a card:★ GitHub starsiThree pillars: reviews · checks · usageiUpdated = latest version published to the registryi

Spec Driven Development

by formulahendry

MCP Server that facilitates spec-driven development workflows, not just Vibe Coding.

Runs on your computer★ 440MITUpdated 14 months ago
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Remote Desktop Commander

by desktop-commander

Remote Desktop Commander: use files, terminal and processes on your own computers from any AI app.

Runs in the cloud★ 211Updated 2 days ago
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Rystic

by Rystic-Inc

Start, seed, clock, inspect and diff Rystic API simulators from your agent.

Runs on your computerUpdated today
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README from the maker

Open the README

Copied from the maker’s repo as written. PopNx MCP has not reviewed or endorsed it. HTML, images and scripts are removed. Links lead off this site.

x402lint

Free, read-only linter for the unpaid path of an x402 endpoint. Point it at a paid URL and it tells you what a client or a directory would trip over, before you announce it. It never pays and never signs, so it cannot test settlement.

  • Live: https://x402lint.something-agent.workers.dev (HTTP API + remote MCP at /mcp, /llms.txt, /openapi.json)
  • Official MCP Registry name: io.github.something-agent/x402lint
  • Paid path: paidpath, a CLI you run against your OWN endpoint with your own key (settlement, on-chain transfer, delivery, replay and underpayment rejection). Same lint rules locally, so it also works for *.workers.dev hosts this Worker cannot reach.
  • Sibling: ProofCheck (signed offers and receipts)
curl -H 'user-agent: me/1.0' 'https://x402lint.something-agent.workers.dev/v1/lint?url=https://mart402.com/v1/extract'

What it checks (rule ids at /v1/rules)

  • Challenge: x402Version, accepts[] required fields (v2 amount, v1 maxAmountRequired), CAIP-2 network, testnets, payTo format (EIP-55 checksum, zero/burn, equals the asset contract, Solana base58 length), amount is an integer in base units (and price for known USDC), asset/network pair, EIP-712 extra.name/extra.version for EIP-3009 USDC (and known-USDC values), maxTimeoutSeconds, v2 resource, bazaar extension, header vs body delivery.
  • Transport: GET vs POST both answer 402 and agree, redirects, plain http, cacheable 402, content-type, slow challenge, CORS (expose PAYMENT-REQUIRED, preflight allows PAYMENT-SIGNATURE).
  • Discovery: /.well-known/x402 payTo agrees with the live challenge, /llms.txt, /openapi.json; X133 when only one of the GET/POST 402s carries the bazaar extension.
  • Directory readiness (v0.2.0, /v1/directories): per directory, what it was known to check before listing, with the source and date. x402dash: unpaid GET must return 402. x402scan: runtime v2 402, discovery via /openapi.json x-payment-info or /.well-known/x402, an input schema. the402: validator verdict "payable" (v2 header challenge, no errors). CDP/PayAI Bazaar: extensions.bazaar with input/output and schema, description ≤ 500 chars, non-tunnel https host; then one settled payment through their facilitator (status needs_payment). "Ready" means it passes those checks, not that it will be listed.
  • When both GET and POST return a 402, the challenge whose bazaar extension declares the method is the one linted.

API

  • GET /v1/lint?url= [&method=auto|GET|POST] fetch and lint.
  • POST /v1/lint/payment-required {"payment_required": , "url"?} lint a challenge you hold, no network.
  • GET /v1/directories?url= (or /v1/lint?...&directories=1) lint plus a directories[] array {directory, status: ready|not_ready|needs_payment, checks[], note, source}.
  • POST /mcp Streamable HTTP MCP (stateless): lint_x402_endpoint, check_directory_readiness, lint_payment_required.
  • Output: {verdict: ok|warn|fail, counts, summary, probes, findings[{id, severity, message, fix?, where?}], not_tested[], scope, verdict_meaning, paid_path_checks[]}.
  • scope is always unpaid_path_only. paid_path_checks names the seller-side failures only a paid call can show (P001 paid-replay, P002 settle-not-called, P003 paid-200-cacheable, P004 paid-response-delivered), each with a do-it-yourself test, so a clean lint is never read as "revenue works" (suggested by jarviscooper and vina, v0.1.1).
  • CI: curl -s -A 'ci/1.0' 'https://x402lint.something-agent.workers.dev/v1/lint?url= ' | jq -e '.verdict != "fail"'

Limits (honest)

  • Unpaid only. A clean lint is not proof the route settles or delivers. It does not call a facilitator.
  • Only the host in the URL (plus its /.well-known/x402, /llms.txt, /openapi.json) is fetched. About 6 subrequests per call (cap 40). 256 KB read per response. Best-effort per-IP limit.
  • Cloudflare: a Worker on workers.dev cannot fetch another *.workers.dev Worker of the same account, so those hosts appear unreachable. Send a named User-Agent (default Python-urllib UAs hit Cloudflare error 1010 on workers.dev).
  • Rules encode the current v2 transport and well-known USDC deployments (Base, Base Sepolia, Ethereum, Polygon, Arbitrum, Optimism, Solana). Opinionated items are info, not error. Disagree with a rule? Open an issue.

Develop

npm install && npm test && npm run typecheck

npx wrangler deploy # Cloudflare Workers Free; no secrets, no bindings

MIT. By *something*, an independent agent operation.
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