legible-check

legible-check — pay-per-call data tools for AI agents (x402 + MCP)

An MCP server and x402 seller that exposes on-chain data tools an agent can call and pay for per request in USDC on Base. No signup, no API key, no subscription: an unpaid call answers HTTP 402 with the price, the payer signs a USDC authorization, and the tool runs.

• MCP endpoint (Streamable HTTP): https://legible-check.ezealfa.workers.dev/mcp
• OpenAPI: https://legible-check.ezealfa.workers.dev/openapi.json
• Health: https://legible-check.ezealfa.workers.dev/health
• Receiving wallet: 0xF3D5de46f73d9f55DFce23F4AAF3Db5505c823c5 (Base)

Connect from an MCP client

{
  "mcpServers": {
    "legible-check": {
      "type": "streamable-http",
      "url": "https://legible-check.ezealfa.workers.dev/mcp"
    }
  }
}

The server answers JSON-RPC 2.0 over POST /mcp, and also in text/event-stream frames when the client sends Accept: text/event-stream.

Methods: initialize, tools/list, tools/call.

Tools

tool	price (USDC)	what it returns
evm_block	0.001	block number, timestamp, base fee, gas used, tx count
evm_gas	0.001	gas price split into base and priority fee
evm_balance	0.002	native balance in wei and native units
evm_token_balance	0.003	ERC20 balance with decimals and symbol
evm_nonce	0.002	next transaction nonce
evm_tx	0.002	decoded transaction by hash
evm_tx_status	0.001	success / reverted / pending with confirmations
evm_receipt	0.002	receipt: status, block, gas used, effective gas price
evm_transfers	0.003	ERC20 transfers for an address over N blocks
evm_token_info	0.002	name, symbol, decimals, total supply
evm_contract	0.003	is-contract check, bytecode size, Sourcify ABI
evm_portfolio	0.005	native balance + nonce + up to 10 token balances in one call
evm_decode	0.003	calldata decoder: selector, signatures, decoded arguments
crypto_price	0.001	live prices with 24h change and market cap
dex_quote	0.002	DEX pair quotes with liquidity and 24h volume
arena_commit_reveal_roll	0.010	cryptographic commit-reveal randomness benchmark verifying SHA-256 deterministic PRNG
security_ai_vault_ctf	0.050	AI red-teaming security challenge (CTF / Bug Bounty): adversarial prompt injection test

Chains: base, polygon, arbitrum (pass ?chain= on HTTP, or chain in the tool arguments).

How payment works

1. Call a tool without payment. The server answers 402 with accepts[]: payTo, amount (atomic USDC, 6 decimals), asset, network (eip155:8453).
2. Sign an EIP-3009 TransferWithAuthorization for that amount.
3. Retry the same request with the PAYMENT-SIGNATURE header containing the base64 payload { x402Version: 2, accepted: <requirement>, payload: { type: "eip3009", signature, authorization } }.
4. The server verifies and settles through the CDP facilitator and returns the data plus a PAYMENT-RESPONSE header with the settlement transaction.

Parameter names are query parameters on HTTP (?address=, ?token=, ?hash=, ?chain=). Unsupported chains are rejected with 400 before any payment is requested.

Why this exists

The agent economy pays per call, but most endpoints are undocumented wrappers with no schema. This server publishes a machine-readable contract: OpenAPI with x-payment-info, an MCP tool list with input schemas, and answers that always state the chain and the block they were read at.

Research & Security Compliance

All tools, benchmarks, and challenges provided by this server are strictly for autonomous AI agent research, cryptographic protocol evaluation, and cybersecurity red-teaming:

• arena_commit_reveal_roll demonstrates deterministic SHA-256 pseudo-random commit-reveal verification.
• security_ai_vault_ctf operates under an open vulnerability research model (Capture The Flag / Bug Bounty). Fees represent inference computation costs and the prize pool acts as an alignment bounty. This server does not operate unlicensed gambling, wagering, or custodial financial services.

License

MIT