smart402 is a risk evaluation service for AI agent payments. This document explains exactly what the SDK sees, what it sends, and what it cannot do — so you can verify these claims by reading the source.

When your agent encounters an x402 payment requirement, the SDK calls POST /evaluate with this data:

{
  "agent_id": "your-agent-id",
  "agent_wallet_address": "0x...",
  "agent_framework": "langchain",
  "wallet_provider": "local_evm",
  "sdk_version": "0.1.0",
  "payment_requirements": {
    "amount": "0.10",
    "token": "USDC",
    "network": "eip155:8453",
    "pay_to": "0x9dBA414637c611a16BEa6f0796BFcbcBdc410df8",
    "scheme": "exact",
    "description": "Weather data — 1 request"
  }
}

All of these fields are visible to the counterparty or the x402 protocol anyway. The pay_to address is public. The amount and token are in the payment requirement served by the seller. The agent_wallet_address is the public key, not the private key.

• Private keys — the SDK never asks for them, never touches them
• Wallet seed phrases — same
• Signed transactions — signing happens after smart402 approves, in your wallet/signer
• Raw transaction data — smart402 evaluates payment requirements, not signed transactions
• Wallet balances — not requested, not sent
• Other agent state — only the fields above

You can verify this by reading the source:

• Python: smart402/client.py — the only outbound HTTP call
• Python: smart402/guard.py — what gets extracted from x402 requirements
• Python: smart402/models.py — the exact request schema

Or proxy the SDK's HTTP calls with mitmproxy and inspect what goes over the wire.

• Return approve or deny for a payment
• Log the evaluation: amount, token, counterparty address, decision, latency
• Update your agent's spend counters for budget enforcement
• Cache counterparty metadata (contract type, wallet age) from public Etherscan data

• Sign transactions — it has no access to your private key
• Initiate payments — it responds to your evaluation requests, never initiates
• Modify payment parameters — it returns an approve/deny decision; your code decides what to do next
• Redirect payments to a different address — the SDK does not modify pay_to
• Access your wallet funds — no key, no access

The SDK is a thin HTTP client. The Python SDK is ~300 lines across 4 files. It does two things:

1. Converts the x402 PaymentRequirements object to the smart402 request format
2. Calls POST /evaluate and returns the response

It does not hook into wallet signing. It does not intercept or modify transactions. It does not hold state between calls beyond configuration. Your agent code decides what to do with the approve/deny response — the SDK does not enforce anything.

Zero network calls beyond the single POST /evaluate. No telemetry, no analytics, no side-channel requests.

You control what happens when smart402 is unreachable:

Set fail_mode="fail_closed" for high-value agents where safety is more important than uptime.

When you use the hosted API at https://streetsmart-api.fly.dev:

Stored per evaluation:

• Amount, token, network, counterparty address (pay_to)
• Decision (approve/deny) and triggered rules
• Latency and timestamp
• Agent ID and account ID (your account, not your private key)

Counterparty cache (shared across accounts for efficiency):

• Whether pay_to is a contract or EOA
• Wallet age in days (derived from first transaction, via Etherscan)
• Whether the contract is verified on Etherscan

Never stored:

• Private keys
• Signed transactions
• Wallet balances
• Any data not listed above

Isolation: All evaluation data is scoped to your account. Other accounts cannot see your evaluations, agents, or policies. Dashboard access is authenticated via Clerk.

1. Read the SDK source — it's ~300 lines of Python. The entire outbound request is in client.py.
2. Proxy the SDK — use mitmproxy or Charles and inspect the actual HTTP call.
3. Check the request schema — models.py defines exactly what gets serialized.
4. Run the tests — pytest tests/ — they use mock HTTP and confirm no unexpected calls are made.