Submit a smart-contract write call from a KMS signer. The gateway encodes via viem, signs the digest via AWS KMS, and broadcasts. Idempotent on optional idempotency_key. Cost: chain gas at-cost + $0.000005 KMS sign fee per call.
AI agents use contract_call to commit financial operations through Run402 — usually the final step of a payment, billing, or trading workflow. A call moves real money.
This tool executes on-chain transactions by signing and broadcasting smart contract calls using a KMS-managed private key. This directly commits financial resources (gas costs + signing fees) and can trigger arbitrary contract logic with real monetary consequences. It spans Execute and Financial categories; Financial is most severe given it moves on-chain assets/state and incurs real costs per invocation.
From the tool's definition Submit a smart-contract write call from a KMS signer... signs the digest via AWS KMS, and broadcasts. Cost: chain gas at-cost + $0.000005 KMS sign fee per call.
Attacks that exploit this kind of access
Submit a smart-contract write call from a KMS signer. The gateway encodes via viem, signs the digest via AWS KMS, and broadcasts. Idempotent on optional idempotency_key. Cost: chain gas at-cost + $0.000005 KMS sign fee per call. It is categorised as a Financial tool in the Run402 MCP Server, which means it involves financial transactions. Block by default and require explicit approval.
Register the Run402 MCP server in PolicyLayer and add a rule for contract_call: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Run402. Nothing to install.
contract_call is a Financial tool with critical risk. Critical-risk tools should be blocked by default and only enabled with explicit human approval.
Yes. Add a rate_limit block to the contract_call rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for contract_call. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
contract_call is provided by the Run402 MCP server (kychee-com/run402). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Every MCP server has a record like this.
Type a name, get the same breakdown: verified identity, auth posture, risk grade, capabilities, recommended policy.
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