get function selector
AI agents call sig to retrieve information from Blockchain MCP Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This is a deterministic cryptographic calculation tool that retrieves or derives information without interacting with blockchain state, making accounts, or executing transactions. It is purely informational and analogous to tools like 'keccak256' or 'event-sig' also present on this server. No blast radius from misuse.
From the tool's definition Tool name 'sig' and description 'get function selector' indicate a pure query operation. Function selectors are read-only identifiers computed from function signatures (typically the first 4 bytes of a keccak256 hash).
Attacks that exploit this kind of access
get function selector. It is categorised as a Read tool in the Blockchain MCP Server MCP Server, which means it retrieves data without modifying state.
Register the Blockchain MCP Server MCP server in PolicyLayer and add a rule for sig: 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 Blockchain MCP Server. Nothing to install.
sig is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the sig 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 sig. 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.
sig is provided by the Blockchain MCP Server MCP server (lienhage/blockchain-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
sig is one line of Blockchain MCP Server's registry record.
The record carries the whole server: verified identity, auth posture, risk grade, every tool classified, recommended policy — re-checked continuously.
Teams ship this data inside their own products. See what a licence covers →