MCP server

Surface Contract: platform API behavior and x402 pre-payment checks

dev.workers.penny-mcamp.penny-surface-contract/surface-contract

Checked 26 Oct 2026, 08:29 UTC · Connected to it and listed its tools

Surface contracts: API behavior evidence, x402 pre-payment check, MCP server preflight

Website

At a glance

Type

MCP server

Publisher

Not verified

Status

Working at last check

Tools

7

Token cost

About 1,554 tokens per request

Sets up in

Claude Code, Claude Desktop, Codex, Gemini CLI, Cursor, VS Code, Antigravity, ChatGPT, OpenAI API, Grok

Last checked

26 Oct 2026, 08:29 UTC

Connect it to your agent

Add to CursorAdd to VS CodeVS Code Insiders

Opens the app, which shows the server and asks you to confirm. For other apps, copy the setup below.

Claude Code

claude mcp add --transport http surface-contract https://penny-surface-contract.penny-mcamp.workers.dev/mcp

Claude Desktop

Settings → Connectors → Add custom connector, and paste the URL.

Codex (config.toml)

[mcp_servers.surface-contract]
url = "https://penny-surface-contract.penny-mcamp.workers.dev/mcp"

Gemini CLI

{"mcpServers":{"surface-contract":{"httpUrl":"https://penny-surface-contract.penny-mcamp.workers.dev/mcp"}}}

Cursor

{"mcpServers":{"surface-contract":{"url":"https://penny-surface-contract.penny-mcamp.workers.dev/mcp"}}}

VS Code

{"servers":{"surface-contract":{"type":"http","url":"https://penny-surface-contract.penny-mcamp.workers.dev/mcp"}}}

Antigravity

agy mcp add surface-contract https://penny-surface-contract.penny-mcamp.workers.dev/mcp

ChatGPT

Settings → Apps & Connectors → Advanced settings: turn on Developer mode, then Create a connector and paste the URL. Which plans can do this varies.

OpenAI API (Responses tools)

{"type":"mcp","server_label":"surface-contract","server_url":"https://penny-surface-contract.penny-mcamp.workers.dev/mcp","require_approval":"always"}

Grok (xAI API tools)

{"type":"mcp","server_label":"surface-contract","server_url":"https://penny-surface-contract.penny-mcamp.workers.dev/mcp"}

Tools

• contribute_discrepancy ~490 tokens
  Report a platform behaviour that contradicts a published claim, or a new claim, with evidence. One-line call: POST /v1/contribute with {contractId, kind, statement, evidence[], reporter, observedAt}. Stored as pending; a published contract is never changed without independent verification. A contrac
• get_integration_recipe ~125 tokens
  Get a plain-text integration recipe for a platform: the order of operations to use it, and a guard clause for every behaviour we measured going wrong, each naming the contract claim behind it. Derived from the contract, so it cannot drift from it.
• get_surface_contract ~128 tokens
  Get the machine-readable surface contract for a platform host (read/write semantics, pending states, rate limits, limits, idempotency, pagination completeness, data portability), each claim carrying its evidence and its verification status.
• list_surface_contracts ~54 tokens
  List the platform surface contracts published in Penny's free registry, with claim counts.
• preflight_mcp_server ~357 tokens
  Run the anonymous MCP handshake against ANY https MCP endpoint you name, right now, and get back a verdict (open / refused / unreachable / initialize-transport-error), the shape of any refusal body, whether the server is stateful (sets Mcp-Session-Id), how many tools tools/list returns, and the guar
• prepay_check ~326 tokens
  Check an x402 route BEFORE you pay it. GET /v1/prepay?url=<the route> makes ONE unpaid GET with no payment header and no credential, and returns one row: the measured HTTP status, the parsed x402 v2 challenge (scheme / network / asset / amount / payTo), whether that challenge is schema-valid exact-o
• verify_surface ~74 tokens
  Run the anonymous conformance checks for a contract now and return verified / failed / unknown / manual / unsupported per claim.

Browse

• Payments
• Food and recipes

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