Canopy — Compliance MCP Server for Call-Bound Capabilities

Canopy is a Model Context Protocol (MCP) server that issues short-lived, verifiable capabilities linking an off-chain policy decision to a specific contract call. Each capability binds a txIntent to a callHash, so only compliant transactions reach the chain. It is not production ready. Do not look at me if it doesn't work, go make it better. I'm just here for the vibes.

Who It's For

• Smart-contract developers that need policy-guarded calls
• Backend engineers building relayers or wallets with pre-flight checks
• Security teams verifying off-chain compliance before execution
• Smart whitelisting without storing info on chain
• For compliance bro's, it's a good way to check KYC/ID etc without storing on chain.

What's Inside

apps/mcp-server

• Express API exposing GET /health/ping, POST /policy/evaluate, POST /capability/issue, and POST /proof/verify
• Loads policy logic from POLICY_WASM_PATH and signs capabilities with ISSUER_ECDSA_PRIVATE_KEY

pkg/attest

• Shared TypeScript library providing the TxIntent type and callHash helper
• Used by both the server and on-chain contracts

contracts

• Solidity CanopyVerifierLib.sol, ERC-2771 forwarder, and venue examples
• Built and tested with Foundry

other

• examples.http request collection
• Documentation and configuration samples

Features

• Short-lived EIP-712 capabilities bound to call hashes
• Pluggable policy evaluation via OPA Wasm or custom logic
• On-chain verification library and compliant forwarder
• MCP tooling for issuance and proof verification

Requirements

• Node.js 20+ (.nvmrc provided)
• pnpm v10 (corepack enable && corepack prepare pnpm@10.0.0 --activate)
• Optional: Foundry for contract builds (curl -L https://foundry.paradigm.xyz | bash && foundryup)
• CLI tools: curl, jq

Quick Start

pnpm install
pnpm -w -F @canopy/attest build
pnpm -w -F mcp-server dev

How It Works

1. Build txIntent (chainId, subject, target, value, selector, args, policyId).
2. POST /policy/evaluate → { decision, artifacts: { callHash, expiry, nonce, capabilitySig } }.
3. Attach proof to the on-chain call; the destination/validator verifies or pre-flights via /proof/verify.

Call Binding

callHash = keccak256(abi.encode(
  chainid, target, subject, selector, value, keccak256(args)
))

Capability (EIP-712)

Domain: { name:"Canopy", version:"1", chainId, verifyingContract: verifier }
Type: CompliantCall(subject, verifier, target, value, argsHash, policyId, expiry, nonce)

Safety

• Short TTL (e.g., 60s), single-use nonce, issuer allowlist
• Normalize inputs: checksummed 0x addresses, 4-byte selector, raw args (no selector)

MCP Tool Mappings

Tool	Description	HTTP Endpoint
health	ping the server	GET /health/ping
policy	evaluate policy & issue capability	POST /policy/evaluate
capability	issue capability directly	POST /capability/issue
proof	verify a capability proof	POST /proof/verify

Example Request

POST /policy/evaluate HTTP/1.1
Content-Type: application/json

{
  "txIntent": {
    "chainId": 1,
    "subject": "0x0000000000000000000000000000000000000001",
    "target": "0x0000000000000000000000000000000000000002",
    "value": "0x0",
    "selector": "0xabcdef01",
    "args": "0x",
    "policyId": "0x42"
  }
}

Response

{
  "decision": "allow",
  "artifacts": {
    "callHash": "0x...",
    "expiry": 0,
    "nonce": "0x1",
    "capabilitySig": "0x..."
  }
}

Roadmap

• Additional capability schemas like EIP-3074
• Persistent storage for issued nonces
• More MCP tools for contract introspection

License

MIT