agent-discovery-mcp

An MCP server that lets your AI coding agent (Claude Code, OpenClaw, Codex, Cursor, etc.) discover and pay on-chain agents registered on ERC-8004, using Coinbase's official x402 protocol.

No smart account. No bundler. No relay. Just your EOA, an HTTPS request, and an automatic 402 → sign → retry flow.

What it does

Three tools, exposed via Model Context Protocol:

| Tool | What it does | Source of truth | |---|---|---| | find_agents_by_skill | Search the ERC-8004 registry for agents matching a skill keyword. Returns id, chain, name, description, endpoint, and x402-support flag. | 8004scan.io public API + semantic search | | get_agent_card | Fetch one agent's full ERC-8004 registration card (name, services, x402 support, trust models, owner address). | 8004scan, falls back to direct RPC | | call_agent_with_payment | HTTP call an agent endpoint. If the agent returns HTTP 402, sign an x402 payment using your EOA and retry — automatically. | x402-fetch (Coinbase official) |

The whole server is ~250 lines of TypeScript. There's no smart contract account, no bundler, no third-party relay involved — payment is direct EOA signing per the x402 spec.

Why this exists

The pieces of an agent-to-agent economy are now real:

• x402 (Coinbase's HTTP 402-based payment protocol) processes 165M+ transactions and ~$50M in volume as of April 2026.
• ERC-8004 (Ethereum's agent identity standard) was deployed to mainnet on January 29, 2026 and now has tens of thousands of registered agents.
• MCP (Anthropic's tool-call protocol) is the de-facto standard for connecting AI coding agents to external capability.

But there was no clean "glue" that lets a Claude Code / OpenClaw / Cursor user just discover and pay an arbitrary on-chain agent from inside their existing tool. Existing options like @azeth/mcp-server bundle ERC-4337 smart accounts and a custom trust layer on top — which forces a bundler/relay dependency that can fail in practice on testnets.

This server skips all of that. It uses:

1. 8004scan public API for agent discovery (the canonical ERC-8004 indexer maintained by the ERC-8004 team)
2. Coinbase's official x402-fetch for payment — wraps native fetch to handle 402s automatically
3. viem for EOA signing — no contract account deployment, no bundler

The result: install, set one env var, and your agent runtime can call any x402 agent in the ERC-8004 registry.

Install

git clone https://github.com/<you>/agent-discovery-mcp
cd agent-discovery-mcp
npm install
npm run build

Set your wallet's private key (this is the EOA that will sign x402 payments):

export TEST_WALLET_KEY=0x...your-64-hex-private-key

macOS LaunchAgent users (e.g. OpenClaw): use launchctl setenv instead, since LaunchAgent processes don't inherit your shell env:

launchctl setenv TEST_WALLET_KEY 0x...

Use with OpenClaw

Add to ~/.openclaw/openclaw.json under mcp.servers:

{
  "mcp": {
    "servers": {
      "agent-discovery": {
        "command": "node",
        "args": ["/absolute/path/to/agent-discovery-mcp/dist/index.js"],
        "env": {
          "TEST_WALLET_KEY": "${TEST_WALLET_KEY}"
        }
      }
    }
  }
}

Then openclaw gateway restart.

Use with Claude Code

Add to .mcp.json in your project root or ~/.claude/mcp_settings.json:

{
  "mcpServers": {
    "agent-discovery": {
      "command": "node",
      "args": ["/absolute/path/to/agent-discovery-mcp/dist/index.js"],
      "env": {
        "TEST_WALLET_KEY": "${TEST_WALLET_KEY}"
      }
    }
  }
}

Use with Cursor / Cline / any MCP-compatible client

Standard MCP stdio server. Point your client at node /path/to/dist/index.js.

Example session

In your AI coding agent, just ask:

Find me 5 agents on Base mainnet that can do text summarization, only ones supporting x402.

The agent will call find_agents_by_skill({ skill_keyword: "summarization", chain_id: 8453, x402_only: true, limit: 5 }) and return real on-chain agents.

Then:

Call agent #25886 at its primary endpoint with the text "...long article...", pay max $0.05 USDC.

The agent calls call_agent_with_payment({ endpoint: "...", payload: { text: "..." }, max_pay_usdc: 0.05, chain_id: 8453 }). If the server responds 402, the EOA signs an EIP-3009 USDC authorization, retries, and returns the result.

Reality check (May 2026)

The infrastructure works. The ecosystem is uneven:

• ERC-8004 registry has ~70k+ agents across chains. Search works well.
• Many agents on-chain set x402Support: true in their metadata but don't actually run an x402 paywall on their endpoint — they accept calls for free or return 404. The x402_supported flag is self-declared; nobody verifies it.
• Most production x402 traffic today flows through Coinbase Agent.market, AWS Bedrock AgentCore, and similar managed platforms. The "permissionless agent discovery from a registry" flow is real but early.

This server lets you participate in that flow today, while it's still small.

Tools reference

find_agents_by_skill

{
  skill_keyword: string;       // e.g. "summarization", "code review", "price feed"
  limit?: number;              // 1-50, default 10
  chain_id?: number;           // e.g. 8453 (Base), 1 (Ethereum), 56 (BSC)
  x402_only?: boolean;         // filter to agents advertising x402 support
}

get_agent_card

{
  agent_id: number;            // ERC-8004 token ID
  chain_id: number;            // e.g. 8453
}

call_agent_with_payment

{
  endpoint: string;            // full HTTPS URL
  payload?: unknown;           // JSON body (omit for GET)
  max_pay_usdc: number;        // max USDC willing to pay, e.g. 0.10
  chain_id?: number;           // settlement chain, default 8453
}

Supported chains

| Chain ID | Network | x402 settlement | Discovery | |---|---|---|---| | 1 | Ethereum Mainnet | ✅ | ✅ | | 8453 | Base Mainnet | ✅ | ✅ | | 56 | BSC | — | ✅ | | 84532 | Base Sepolia | ✅ | ✅ | | 11155111 | Ethereum Sepolia | ✅ | ✅ |

Architecture

┌───────────────────────┐         ┌──────────────────────┐
│  Claude Code /        │  MCP    │  agent-discovery-mcp │
│  OpenClaw / Cursor    │ ──────▶ │  (this server)       │
└───────────────────────┘  stdio  └──────────┬───────────┘
                                              │
                          ┌───────────────────┼───────────────────┐
                          │                   │                   │
                          ▼                   ▼                   ▼
                   ┌────────────┐      ┌────────────┐      ┌─────────────┐
                   │ 8004scan   │      │ Base RPC   │      │ x402-fetch  │
                   │ public API │      │ (fallback) │      │ (Coinbase)  │
                   │ discovery  │      │ tokenURI   │      │ EOA signs   │
                   └────────────┘      └────────────┘      │ EIP-3009    │
                                                          └─────────────┘

No smart-contract account. No bundler. No relay. Your EOA signs, x402-fetch retries, agent's facilitator settles.

Roadmap

• [ ] Endpoint health check before returning agent in find_agents_by_skill (filter out 404 demo deployments)
• [ ] Verify on-chain x402Support claim by probing endpoint for 402 response
• [ ] Multi-chain payment in one call (auto-select cheapest chain for USDC)
• [ ] Optional integration with Coinbase Facilitator for settlement metadata
• [ ] Spending-limit policy (server-side cap independent of max_pay_usdc parameter)
• [ ] Receipt logging to disk for tax/audit

License

MIT