verify-mcp

An MCP (Model Context Protocol) server that gives any agent a verification tool it can trust: SHA-256 artifact checks and Base USDC transfer decoding, answered by a live API that recomputes hashes server-side and returns PASS / PARTIAL / FAIL.

Built for agents that have to prove a deliverable instead of asserting it — bounty submissions, paid API calls, payout reconciliation, artifact handoffs.

• Transport: stdio (JSON-RPC 2.0), Node.js 20+

• Runtime deps: @modelcontextprotocol/sdk only

• Free: health

• Paid: verify_artifact, verify_base_tx — 0.10 USDC per call on Base via x402 (no account, no API key, no signup — the payment is the auth)

Tools

verify_artifact (paid)

Recompute a SHA-256 digest server-side and compare it with the claim.

{
  "path": "dist/report.pdf",
  "sha256": "9f2c…64 hex chars…",
  "size_bytes": 1048576
}

Optional content_b64 lets you send the bytes inline instead of a path.

Returns { verdict, items[], report } — verdict is PASS when every item matches, PARTIAL when some do, FAIL otherwise.

verify_base_tx (paid)

Decode the USDC Transfer log of a Base transaction and check it against what you expected.

{
  "tx_hash": "0x…64 hex chars…",
  "expect_to": "0x5033036702CCeeE23b79022e938a41e0452F908a",
  "expect_usdc": "0.10"
}

Use this to prove you actually paid — or that someone actually paid you.

health (free)

Liveness + current pricing probe. Useful as a preflight before spending 0.10 USDC.

Related MCP server: ArtifactGuard

Install

Claude Desktop

Add this to claude_desktop_config.json:

• macOS: ~/Library/Application Support/Claude/claude_desktop_config.json

• Windows: %APPDATA%\Claude\claude_desktop_config.json

• Linux: ~/.config/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "verify": {
      "command": "npx",
      "args": ["-y", "github:ciperx/verify-mcp"],
      "env": {
        "VERIFY_API_BASE_URL": "https://agent.ggez.my.id"
      }
    }
  }
}

Restart Claude Desktop. health works immediately; verify_artifact and verify_base_tx return the x402 challenge until you add a payment header (below).

Claude Code / any generic MCP client (stdio)

{
  "mcpServers": {
    "verify": {
      "command": "node",
      "args": ["/absolute/path/to/verify-mcp/src/server.js"],
      "env": {
        "VERIFY_API_BASE_URL": "https://agent.ggez.my.id"
      }
    }
  }
}

From a checkout:

git clone https://github.com/ciperx/verify-mcp
cd verify-mcp
npm install          # only @modelcontextprotocol/sdk
node src/server.js   # speaks JSON-RPC on stdin/stdout

Cursor / Windsurf / Cline

Same mcpServers block, in the editor's MCP settings file (~/.cursor/mcp.json for Cursor).

Paying for a call (x402)

The paid tools never invent a verdict. If X402_PAYMENT_HEADER is not set, they return a structured result like this instead:

{
  "error": "payment_required",
  "http_status": 402,
  "price_usdc": "0.10",
  "amount_atomic": "100000",
  "asset": "0x833589fCD6eDb6E08f4c7C32D4f71b54bdA02913",
  "pay_to": "0x5033036702CCeeE23b79022e938a41e0452F908a",
  "scheme": "exact",
  "network": "base",
  "message": "Payment required: this tool call costs 0.10 USDC on Base…",
  "how_to_pay": { "env_var": "X402_PAYMENT_HEADER", "max_timeout_seconds": 300 },
  "raw_402_body": { "x402Version": 1, "accepts": [ … ] }
}

Flow:

1. Call the tool. Read raw_402_body.accepts[0] (or just pay_to / amount_atomic).

2. Send exactly 100000 atomic USDC on Base to 0x5033036702CCeeE23b79022e938a41e0452F908a.

3. Build the x402 X-PAYMENT payload with your wallet/facilitator and base64-encode it.

4. Export it and restart the server:

export X402_PAYMENT_HEADER="<base64 x402 payment payload>"

5. Call the tool again — that call is served and you get the real verdict.

X402_PAYMENT_HEADER is read per request, so a long-running server picks up a refreshed header on the next call without a restart if you start it from a wrapper that re-reads the env. Each paid call consumes one payment.

A 402 returned after a payment was sent is reported honestly (payment_header_sent: true, "still answered 402") — the header was stale, underfunded, or addressed to the wrong recipient. It is never upgraded to a fake pass.

Configuration

Tests

npm test

12 offline tests, no network required — fetch is injected:

• health hits /verify-api/health and parses pricing

• verify_artifact without a payment header returns a structured 402 with price/asset/payTo/raw body and no verdict

• verify_artifact sends X-PAYMENT and passes the PASS verdict through

• digests are lowercased, size_bytes forwarded

• verify_base_tx 402 path and 200 verdict path

• invalid path / sha256 / tx_hash rejected before any network call

• upstream 500 and ECONNREFUSED reported as errors, not verdicts

• 402-after-payment explained, never faked

• challenge parser handles v1 maxAmountRequired and v2 amount

• tool catalog is exactly the three documented tools

• end-to-end stdio test: initialize handshake, tools/list, unknown-tool error

Layout

src/core.js     API client: fetch injection, 402 challenge parser, payload builders
src/server.js   MCP server: tool schemas + handlers over stdio
test/           12 offline tests (node:test)
mcp.json        server manifest read by MCP directories
smithery.yaml   Smithery deployment config
SHA256SUMS.txt  checksums of the published files

License

MIT