tctc-mcp

An MCP server exposing ERC-7303 (Token-Controlled Token Circulation) roles to AI agents: agents check their own on-chain permissions, and human principals grant/revoke them by minting/burning control tokens — no permission server required.

Status: v0.3 — adds timed roles with gasless auto-expiry (below), on top of v0.2's IERC7303 auto-discovery; published on npm (tctc-mcp), unit-tested and verified end-to-end against the Sepolia demo deployment (grant → check → revoke → check, and grant-for-75s → auto-expiry, through a real MCP client).

Demo (60 seconds)

A human grants an AI agent a minting permission; the agent verifies it on-chain and mints an NFT. The human burns the role token — and the agent instantly loses the capability. Live on Sepolia, no permission server involved.

Related MCP server: ows-mcp-wallet

Quick start

The package is published on npm, so no clone or build is needed — npx fetches and runs it directly:

# 1. Get a config. The secret-free Sepolia demo config needs no API keys:
curl -fsSLO https://raw.githubusercontent.com/kofujimura/tctc-mcp/main/examples/config.sepolia.agent.json

# 2. Register with your MCP client, e.g. Claude Code
#    (read-only mode: only query tools are registered)
claude mcp add tctc -- npx -y tctc-mcp --config "$PWD/config.sepolia.agent.json"

# Admin mode (principal side): grant_role / revoke_role also registered.
# Provide the issuer key ONLY via the environment:
claude mcp add tctc-admin --env TCTC_ADMIN_PRIVATE_KEY=0x... \
  -- npx -y tctc-mcp --config "$PWD/config.sepolia.json"

Or in a project-scoped .mcp.json:

{ "mcpServers": { "tctc": { "command": "npx",
    "args": ["-y", "tctc-mcp", "--config", "examples/config.sepolia.agent.json"] } } }

A fuller registration example is in examples/claude.mcp.json. The admin private key is only ever read from the TCTC_ADMIN_PRIVATE_KEY environment variable; configs containing anything that looks like a private key are rejected at startup.

Tools

* registered only when the config has an identity section.

Subjects can be given as a raw address, as an ERC-8004 agentId (resolved to its ERC-6551 Token Bound Account, the recommended binding target), or omitted to use the config's self.

IERC7303 auto-discovery (v0.2)

ERC-7303 now defines an introspection interface (ethereum/ERCs#1872, merged 2026-07-11): compliant contracts expose hasRole, control-token getters, configuration events, and ERC-165 detection (interfaceId 0x4ee69337). tctc-mcp uses it two ways:

• target roles — a role config names only the target contract; the server reads which control tokens gate the role from the contract itself, and the verdict is the target's own hasRole() answer:

  "roles": { "MINTER_ROLE": {
      "target": { "address": "0x4C0a78803D47154B9C6F42EC4AEbab2D1C94c97D" } } }

• discover_roles — introspect any address at run time, with no role configuration at all. Non-compliant contracts report supportsIERC7303: false; static controlTokens configs remain the fallback for pre-IERC7303 deployments.

Working example: examples/config.sepolia.discovery.json (secret-free, public RPC), verified live by scripts/e2e-discovery.mjs.

Timed roles: gasless auto-expiry (v0.3)

Delegation to an agent is usually short-term — "mint for one hour", "act for the duration of this task". With an expiring control token (ExpiringControlTokens), balanceOf() returns 0 once the holder's expiry passes, so the role revokes by itself, with no transaction — even if the principal forgets, goes offline, or loses keys. The ERC-7303 target contract needs no changes at all (the Sepolia expiry demo target is a byte-for-byte copy of TCTCDemoToken).

• Granting: a role whose grant template has $expiresAt requires an expiry — grant_role with expiresInSeconds: 3600 is "grant MINTER_ROLE for one hour":

  "admin": { "grant": { "function": "mint(address,uint256,uint64)",
                        "args": ["$subject", "$typeId", "$expiresAt"] } }

• Checking: check_role evidence reports expiresAt (unix seconds) when the control token exposes it, so an agent can self-report "this permission expires in 5 minutes".

• Kill switch unchanged: expiry is a fail-safe, not a replacement — revoke_role (issuer burn) still revokes immediately within the validity window.

Working example: the TIMED_MINTER_ROLE in examples/config.sepolia.json, verified live by scripts/e2e-expiry.mjs (grant for 75 s → watch it expire with no further transaction).

Documents

• docs/CONCEPT.md — background and rationale: TCTC as the authorization layer for AI agents, its relationship to ERC-8004 (Trustless Agents) and ERC-6551 (Token Bound Accounts), recommended ERC-7303 spec updates, and the adoption strategy.

• docs/MCP_SERVER_SPEC.md — v1 design specification (architecture, config, tools, security, roadmap).

• docs/ERC_DRAFT_EXPIRABLE_1155.md — working draft of a planned ERC, "Expirable ERC-1155 Tokens": the standard behind the timed roles above (per-holder expiry, time-aware balanceOf, expiresAt/ExpiryUpdated, interface ID 0x300e616b). Not yet submitted to ethereum/ERCs; feedback welcome.

• docs/TEST_REPORT.md — v1 test report: 24 unit tests and the live Sepolia E2E (on-chain kill-switch cycle through a real MCP client).

• examples/config.sepolia.json — concrete config for the Sepolia demo deployment (primary roles, static bindings) and the TCTC repo's MyComplexToken sample (COMPLEX_* roles, resolved via IERC7303 target discovery).

• examples/config.sepolia.agent.json — secret-free agent-side config for the same demo deployment (public RPC, no API keys); the one used in the Quick start above.

• examples/config.sepolia.discovery.json — IERC7303 auto-discovery variant: no control tokens configured, the target contract explains its own role structure.

• examples/contracts/ — sources of the demo contracts deployed on Sepolia (AgentControlTokens, TCTCDemoToken, ERC7303, IERC7303).

Demo deployment (Sepolia, Etherscan-verified)

• AgentControlTokens (soulbound, issuer-burnable ERC-1155): 0x12342A7F0190B3AF3F4b47546D34006EDA54eE0B

• TCTCDemoToken (ERC-721 + ERC-7303 target, implements the IERC7303 introspection interface — hasRole, control-token getters, ERC-165 detectable via interfaceId 0x4ee69337): 0x4C0a78803D47154B9C6F42EC4AEbab2D1C94c97D

• ExpiringControlTokens (soulbound, issuer-burnable ERC-1155 with per-holder expiry; time-aware balanceOf — the basis of timed roles): 0xb5abB6c060ed287e8B25aD121c8B46eE404fF09b

• Expiry demo target (unmodified TCTCDemoToken bytecode bound to the expiring control tokens): 0x3eAb11DE9655817A2e2977A486d9D33eBD10c9Ce

Development

git clone https://github.com/kofujimura/tctc-mcp.git && cd tctc-mcp
npm install && npm run build
node dist/index.js --config examples/config.sepolia.agent.json

npm test                  # unit tests (vitest)
node scripts/e2e-live.mjs # live E2E: spawns the server via MCP stdio client
                          # (needs ALCHEMY_API_KEY; admin phase additionally
                          #  TCTC_ADMIN_PRIVATE_KEY and E2E_SUBJECT)

Related

• npm package: https://www.npmjs.com/package/tctc-mcp

• Agent skill (teaches agents to use TCTC safely; install with npx skills add kofujimura/tctc-skills): https://github.com/kofujimura/tctc-skills

• TCTC reference implementation: https://github.com/kofujimura/TCTC