Compute the selector/topic hash for a function/error/event signature locally (keccak256, no RPC). WHEN TO CALL: (1) BEFORE passing raw calldata to simulate_transaction — build `0x<selector><encoded args>` instead of guessing; (2) BEFORE calling get_logs with raw `topics` — compute topic0 from the...
Part of the Kosyak Evm MCP server. Enforce policies on this tool with Intercept, the open-source MCP proxy.
AI agents invoke compute_selector to trigger processes or run actions in Kosyak Evm. Execute operations can have side effects beyond the immediate call -- triggering builds, sending notifications, or starting workflows. Rate limits and argument validation are essential to prevent runaway execution.
compute_selector can trigger processes with real-world consequences. An uncontrolled agent might start dozens of builds, send mass notifications, or kick off expensive compute jobs. Intercept enforces rate limits and validates arguments to keep execution within safe bounds.
Execute tools trigger processes. Rate-limit and validate arguments to prevent unintended side effects.
tools:
compute_selector:
rules:
- action: allow
rate_limit:
max: 10
window: 60
validate:
required_args: trueSee the full Kosyak Evm policy for all 43 tools.
Agents calling execute-class tools like compute_selector have been implicated in these attack patterns. Read the full case and prevention policy for each:
Other tools in the Execute risk category across the catalogue. The same policy patterns (rate-limit, validate) apply to each.
compute_selector is one of the high-risk operations in Kosyak Evm. For the full severity-focused view — only the high-risk tools with their recommended policies — see the breakdown for this server, or browse all high-risk tools across every MCP server.
Compute the selector/topic hash for a function/error/event signature locally (keccak256, no RPC). WHEN TO CALL: (1) BEFORE passing raw calldata to simulate_transaction — build `0x<selector><encoded args>` instead of guessing; (2) BEFORE calling get_logs with raw `topics` — compute topic0 from the event signature (get_logs also accepts `eventSignature` directly, but if you need multiple topics or to verify topic0 first, use this); (3) to match an unknown 4-byte revert selector against a suspected signature. Input can be full Solidity (`function transfer(address to, uint256 amount)`) or canonical (`transfer(address,uint256)`). Events → full 32-byte topic0; functions/errors → first 4 bytes.. It is categorised as a Execute tool in the Kosyak Evm MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.
Add a rule in your Intercept YAML policy under the tools section for compute_selector. You can allow, deny, rate-limit, or validate arguments. Then run Intercept as a proxy in front of the Kosyak Evm MCP server.
compute_selector is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.
Yes. Add a rate_limit block to the compute_selector rule in your Intercept 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 Intercept policy for compute_selector. 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.
compute_selector is provided by the Kosyak Evm MCP server (kosyak-evm-mcp-server). Intercept sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Open source. One binary. Zero dependencies.
npx -y @policylayer/intercept