CounterpartyCheck

Is it safe for your agent to pay this address? Pre-payment due diligence for AI agents over x402: before paying, approving or interacting with an EVM (Base, Ethereum, Polygon, Arbitrum One) or Solana address, one call returns ok / caution / block with reasons, a confidence and missing_data.

• Live: https://api.youraitools.co/counterpartycheck (also https://counterparty.agentgate.workers.dev)
• Paid (USDC on Base or Solana; Polygon and Arbitrum One also accepted; x402 v2 and v1, or a prepaid credits key):
  • GET|POST /v1/lite $0.005: OFAC SDN + ScamSniffer + x402 Bazaar payee directory + labels + what the address is (wallet, contract, token contract, Safe, EIP-7702, Solana mint / program / token account, USDC readiness)
  • GET|POST /v1/quick $0.015: lite + Sourcify verification and deployer screening, ENS / Basename (forward-verified), cross-chain presence (wrong-chain protection), Safe owner / contract owner / delegate screening, Blockscout tags
  • GET|POST /v1/full $0.05: quick + age, recent activity and exposure to listed addresses, recent approvals to the address (drainer pattern), TokenVerdict for Base tokens
• Free: GET /v1/preview (verdict, confidence, kind, flag counts; 10/min per IP), remote MCP POST /mcp (check_counterparty), /openapi.json, /.well-known/x402, /v1/stats.

Parameters: address (required), chain = base | ethereum | polygon | arbitrum | solana (default base; base58 implies solana), intent = pay | approve | interact (default pay).

curl -s "https://api.youraitools.co/counterpartycheck/v1/preview?address=0x098B716B8Aaf21512996dC57EB0615e2383E2f96&chain=ethereum"
curl -i "https://api.youraitools.co/counterpartycheck/v1/quick?address=0x...&chain=base&intent=pay"   # 402 terms; any x402 client pays
curl -s -H "Authorization: Bearer $YATC_KEY" "https://api.youraitools.co/counterpartycheck/v1/quick?address=0x..."   # prepaid credits

MCP

{ "mcpServers": { "counterpartycheck": { "type": "http", "url": "https://api.youraitools.co/counterpartycheck/mcp" } } }
{ "mcpServers": { "counterpartycheck": { "command": "npx", "args": ["-y", "@agentgate-builder/counterpartycheck"] } } }

The stdio server returns the free preview. Set COUNTERPARTYCHECK_X402_PRIVATE_KEY (a Base wallet with a little USDC; needs @x402/fetch, @x402/evm, viem) and it pays the quick report per call ($0.015, at most $0.02 per payment, only to our payTo). Docker: docker build -t counterpartycheck-mcp . && docker run -i --rm counterpartycheck-mcp.

How it degrades

Every optional source (Sourcify, Blockscout, ENS / Basename, other chains, archive RPCs, TokenVerdict) has a tight timeout. A failed source is listed in missing_data and lowers confidence; it never reads as a clean result. If the chain RPC itself is down, paid routes answer 503 and nothing is charged. Malformed input is a 400 before the 402.

Data and licenses

Free public data only: bundled OFAC SDN snapshot (from PayGuard), ScamSniffer scam-database addresses, a CDP x402 Bazaar catalog snapshot, public RPCs (read-only), Sourcify, Blockscout public API, TokenVerdict. Code: MIT. src/data/scamsniffer.js is ScamSniffer data under GPL-3.0 (https://github.com/scamsniffer/scam-database), redistributed unmodified as a lookup set. Rebuild snapshots: python3 scripts/build-data.py.

A safety check only: no price data, no trading signals. Automated signals, not legal, compliance or financial advice; "ok" means no known risk signal was found, not a guarantee.