Koskamo

x402lint MCP

A free, read-only linter for the unpaid path of an x402 endpoint. It checks the 402 challenge, payTo/asset/amount sanity, EIP-712 hints, redirects, cache, CORS, and discovery files without paying or signing. It helps agents verify directory readiness and transport configuration before announcing a paid URL.

Endpoint and access

No sign-in to connect and list tools. Individual tools may still need a vendor account, credentials, or permissions; check the documented prerequisites.

x402lint MCP logo, by somethingCommunity listingStreamable HTTPNo sign-inEndpoint checked 2026-11-01Published by something
MCP endpoint (Streamable HTTP)
https://x402lint.something-agent.workers.dev/mcp
Vendor documentation

What you can do with it

  • Lint a 402 challenge URL to check version, accepts, and payTo sanity
  • Verify directory readiness by checking x402dash and x402scan compatibility
  • Check CORS and cache headers for compliance with RFC 9111
  • Validate discovery files like /.well-known/x402 and openapi.json

Source and maintenance

Community listingRegistry 0.2.0
mcp-registry: io.github.something-agent/x402lint@0.2.0Source repositoryProject website
Maintenance checked

Protocol and capabilities

Server
x402lint 0.2.5
MCP protocol
2025-06-18
Tools
3 advertised
Resources
Not advertised
Resource templates
Not advertised
Prompts
Not advertised
Server-advertised capabilities
{
  "tools": {
    "listChanged": false
  }
}

Server-provided instructions

Untrusted server output shown for inspection. It is not Koskamo guidance and is excluded from knowledge search.

Free, read-only lint of an x402 endpoint's unpaid 402 path. Never pays or signs; it cannot test settlement.

Tools

3 advertised

lint_x402_endpoint
Advertised by the server during the last successful anonymous check.

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 findings with ids, severities and fixes. Never pays. Free.

lint_x402_endpoint input schema
{
  "type": "object",
  "required": [
    "url"
  ],
  "properties": {
    "url": {
      "type": "string",
      "description": "The paid x402 URL"
    },
    "method": {
      "enum": [
        "auto",
        "GET",
        "POST"
      ],
      "type": "string",
      "description": "Default auto: tries both"
    }
  }
}
check_directory_readiness
Advertised by the server during the last successful anonymous check.

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 <= 500 chars, non-tunnel https host; listing then needs one settled payment) were known to check. Never pays. Free.

check_directory_readiness input schema
{
  "type": "object",
  "required": [
    "url"
  ],
  "properties": {
    "url": {
      "type": "string",
      "description": "The paid x402 URL"
    },
    "method": {
      "enum": [
        "auto",
        "GET",
        "POST"
      ],
      "type": "string",
      "description": "Default auto: tries both"
    }
  }
}
lint_payment_required
Advertised by the server during the last successful anonymous check.

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.

lint_payment_required input schema
{
  "type": "object",
  "required": [
    "payment_required"
  ],
  "properties": {
    "url": {
      "type": "string",
      "description": "Optional: the URL it was served from, to check resource.url"
    },
    "payment_required": {
      "description": "Object, JSON string, or base64 header value"
    }
  }
}

Prompts

Not advertised

No prompt definitions available.

Resources

Not advertised

No resource definitions available.

30-day availability

Aggregated from read-only remote checks; this is not a tool-execution or security guarantee.

Successful checks
1 of 1 (100%)
Average latency
170 ms
95th percentile latency
170 ms

Maintenance history

Public check and source-refresh events. Editorial and ownership records remain private.

  • · probe · passed · 170 ms · metadata changed · 3 tool(s)

Connect from your client

Each snippet registers the same endpoint; pick the client you use.

This server is operated by the named third party. Listing and endpoint checks are not an endorsement or a security audit. Review the operator's permissions, terms, and data handling before connecting. How listings are checked and corrected.

Claude Code

Run this once in a terminal. It registers the remote server. Use --scope project to write .mcp.json for the repo.
Claude Code configuration
claude mcp add --transport http x402lint-mcp-workers https://x402lint.something-agent.workers.dev/mcp

Codex

Run this once. Codex stores MCP servers in ~/.codex/config.toml (or .codex/config.toml in a trusted project).
Codex configuration
codex mcp add x402lint-mcp-workers --url https://x402lint.something-agent.workers.dev/mcp

Cursor

Merge this server into .cursor/mcp.json in your project, then enable x402lint-mcp-workers in your MCP settings.
Cursor configuration
{
  "mcpServers": {
    "x402lint-mcp-workers": {
      "url": "https://x402lint.something-agent.workers.dev/mcp"
    }
  }
}

Cline

Merge this into cline_mcp_settings.json (Cline → MCP Servers → Configure).
Cline configuration
{
  "mcpServers": {
    "x402lint-mcp-workers": {
      "type": "streamableHttp",
      "url": "https://x402lint.something-agent.workers.dev/mcp",
      "disabled": false
    }
  }
}

VS Code

Merge this server into .vscode/mcp.json. Use MCP: List Servers to start x402lint-mcp-workers and inspect its tools.
VS Code configuration
{
  "servers": {
    "x402lint-mcp-workers": {
      "type": "http",
      "url": "https://x402lint.something-agent.workers.dev/mcp"
    }
  }
}

Gemini CLI

Run this once. It writes .gemini/settings.json in the current project; pass --scope user for ~/.gemini/settings.json.
Gemini CLI configuration
gemini mcp add --transport http x402lint-mcp-workers https://x402lint.something-agent.workers.dev/mcp

Claude Desktop

Merge this into claude_desktop_config.json (macOS: ~/Library/Application Support/Claude/, Windows: %APPDATA%\Claude\), then restart Claude Desktop.
Claude Desktop configuration
{
  "mcpServers": {
    "x402lint-mcp-workers": {
      "url": "https://x402lint.something-agent.workers.dev/mcp"
    }
  }
}

Windsurf

Merge this into ~/.codeium/windsurf/mcp_config.json, then refresh MCP in Cascade. Windsurf remote servers use serverUrl, not url.
Windsurf configuration
{
  "mcpServers": {
    "x402lint-mcp-workers": {
      "serverUrl": "https://x402lint.something-agent.workers.dev/mcp"
    }
  }
}

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