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

Connect Remote server

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

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

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

Settings > Connectors > Add custom connector
URL: https://penny-surface-contract.penny-mcamp.workers.dev/mcp

Tools 7 found in our last check

• list_surface_contracts

  List the platform surface contracts published in Penny's free registry, with claim counts.

• get_surface_contract

  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.

• verify_surface

  Run the anonymous conformance checks for a contract now and return verified / failed / unknown / manual / unsupported per claim.

• contribute_discrepancy

  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 ve…

• get_integration_recipe

  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.

• preflight_mcp_server

  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…

• prepay_check

  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…

Details

More finance and crypto servers See all

• RightCard

  Which of your credit cards to use at any store, from verified bank data. No bank login.

• Africa Compliance Data

  African holidays, business days, VAT, withholding tax, tax treaties, tax IDs and filing deadlines

• BusCalc Business Calculators

  Business calculators, data lookups, replayable receipts, and documentation for enterprise pilots.

• CarLoanMath

  US car loan math: monthly payment, compare loans, max price for your budget, amortization. Free.

• InfinityVolume

  Dollar volume across 13 stock markets and US sectors, against each one's own normal. No prices.

• xytara MCP Executor

  Pay-per-call MCP tools and signed on-chain attestations: 20 free/day, then x402 or a spend key.