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

by workers-penny-mcamp-penny-surface-contract Your server? Claim it

answering

Surface Contract: platform API behavior and x402 pre-payment checks is answering right now. Last checked 4 min ago. It exposes 7 tools.

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

Uptime history 13 days of history

13 days agonow

100.0%

Uptime 24h

91 of 91 checks

Tools

read from the server

476 ms

Response time

average over 24h

open, no key

Access

streamable-http

What changed 8

Every tool that appeared, vanished or quietly changed what it asks for. Recorded since 15 October 2026. No other catalogue keeps this.

15 Oct 2 tool descriptions were rewritten4 times that day contribute_discrepancy, preflight_mcp_server

15 Oct 2 tools appeared preflight_mcp_server, prepay_check

15 Oct 2 tools changed the parameters they ask for contribute_discrepancy, preflight_mcp_server

and 2 more, back to 15 October 2026

Nothing serious here today

Today is the operative word: we check Surface Contract: platform API behavior and x402 pre-payment checks every 15 minutes and re-read its code on every release. Watch it and you find out the day that stops being true.

Connect this server

Endpoint below is the one we actually reach during checks — not the one copied from a README. Last verified 4 min ago.

Claude Code Claude Desktop Codex Cursor VS Code

run in your terminal

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

Settings → Connectors → Add custom connector, then paste this address

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

~/.codex/config.toml

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

.cursor/mcp.json

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

.vscode/mcp.json

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

Available tools 7

Read directly from the server with tools/list, grouped by what they act on. If a tool disappears, we record the date.

surface

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.

list_surface_contracts

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

contribute

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 verification. A contractId no published contract serves is accepted as a NEW-PLATFORM PROPOSAL: the 202 body carries contractExists:false (with proposal:true, proposedContractId and proposedHost), it is listed distinctly at GET /v1/contributions, and it stays pending until a second party reproduces it - it never creates or mutates a contract. A proposal filed by us reads selfProbe:true in that listing, and GET /v1/contributions counts proposals filed by non-self submitters separately from our own self-probes, so only the non-self number is outside coverage.

integration

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

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 returns, and the guard clauses that follow. Use it before wiring an MCP server into your own config. Pass `urls` (up to 5) to check a whole mcp.json in one call. When the endpoint refuses, it also reports whether the refusal advertises a credential path (an RFC 9728 resource_metadata pointer) and whether that pointer resolves to a metadata document naming an authorization server, so you learn where a token would come from without writing that parsing yourself. No credential is sent, none is obtained, and none of their tools is ever called.

prepay

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 schema-valid exact-on-Base, and whether its payTo and price agree with the seller's own card (pass `card` to read that card with one more unpaid GET). No payment is made, no credential is sent, no redirect is followed, and a transport failure on our side is reported as unknown rather than as a fact about the seller. Use it to gate a payment decision on measured terms instead of on a seller's prose.

verify

verify_surface

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

Endpoints

URL	Transport	State	Latency	Checked
https://penny-surface-contract.penny-mcamp.workers.dev/mcp	streamable-http	answering	424 ms	4 min ago

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

Answers built from our own checks of this server.

What can Surface Contract: platform API behavior and x402 pre-payment checks do?

It exposes 7 tools, read directly from the server on our last check. Among them: contribute_discrepancy, get_integration_recipe, get_surface_contract, list_surface_contracts, preflight_mcp_server, prepay_check and 1 more. The full list with descriptions is on this page — we take it from the server itself via tools/list, not from a README. How MCP servers expose tools in the first place →

Is Surface Contract: platform API behavior and x402 pre-payment checks working right now?

We send a real MCP handshake every 15 minutes. Over the last 24 hours 91 of 91 checks got a reply (100.0%), average response time 476 ms. The bar chart above shows every period we have measured.

How do I connect Surface Contract: platform API behavior and x402 pre-payment checks?

Copy the ready config from this page. We generate it for Claude Code, Claude Desktop, Codex, Cursor and VS Code, each in the form that client actually reads. It is a remote server, so there is nothing to install — the client connects to the address.

Does Surface Contract: platform API behavior and x402 pre-payment checks need an API key?

No. Surface Contract: platform API behavior and x402 pre-payment checks completed a full MCP handshake with us as an anonymous client and listed its tools without asking for anything. All 7 of them are readable on this page. This is what we observed, not what the docs claim.

How fast is Surface Contract: platform API behavior and x402 pre-payment checks?

It answers our handshake in 476 ms on average, which is faster than 28% of all working MCP servers we measure. The comparison comes from our own checks across the whole registry, every 15 minutes.