AI agents call search_stations to retrieve information from Metro MCP without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool retrieves or queries static Metro station information (name, code) without creating, modifying, deleting, or executing any operations. It is a straightforward read-only lookup that presents no risk of unintended data modification or system state changes. Low severity reflects minimal blast radius if misused by an AI agent.
From the tool's definition Tool name 'search_stations' and description 'Search for Metro stations by name or code' indicate a query/retrieval operation with no modification of data or external effects.
Attacks that exploit this kind of access
Search for Metro stations by name or code. It is categorised as a Read tool in the Metro MCP MCP Server, which means it retrieves data without modifying state.
Register the Metro MCP server in PolicyLayer and add a rule for search_stations: 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 Metro MCP. Nothing to install.
search_stations 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 search_stations 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 search_stations. 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.
search_stations is provided by the Metro MCP server (nathanielnoyd/metro-mcp). 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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