b20check-mcp

An MCP (Model Context Protocol) server for B20 Check. It lets Claude, ChatGPT, or any MCP client verify a B20 token on Base before you touch it: you ask, in plain language, whether a token is safe, and your assistant runs the check and reads you the signed verdict.

What it exposes

• verify_b20_token(address) — is this address a legitimate B20 token on Base, and what powers does its issuer hold? Returns a verdict (ok / caution / danger), risk flags (mint, freeze, seize, pause, admin, impostor, and more), data freshness (indexed / live / not_indexed), and an EIP-712 signed attestation you can verify independently. A token that cannot be fully checked is never signed as a clean pass.
• b20_stats() — how many B20 tokens B20 Check has indexed.

The tool description instructs the assistant to run the check before helping move value into a B20 token it has not already verified.

Add to Claude Desktop

In claude_desktop_config.json:

{
  "mcpServers": {
    "b20-check": {
      "command": "npx",
      "args": ["-y", "b20check-mcp"]
    }
  }
}

No-code alternative (no install): B20 Check also runs a remote MCP connector. Paste https://b20check.com/mcp into Claude (Settings, Connectors) or add it in ChatGPT as a custom MCP connector.

Free vs paid

By default this server calls the free, rate-limited demo route (20 checks/minute, no wallet, no keys). For unmetered access, set B20_AGENT_KEY to a Base private key that holds USDC; the server then pays $0.01 per call via x402 through the paid /v1/verify endpoint.

| Env | Default | Meaning | |-----|---------|---------| | B20_BASE_URL | https://b20check.com | B20 Check API base URL | | B20_AGENT_KEY | (unset) | 0x Base key holding USDC; enables paid, unmetered access via x402 |

Verify-don't-trust: the attestation is EIP-712 signed. Recover the signer (0x1388d1e3751512955A53C7c2795Eaf8a3B029e6A) from the signature yourself rather than trusting the verdict field alone.

MIT licensed.