Get real-time arrival information for trains at a specific station, including platform numbers, delays, origin stations, and any relevant travel notes. Returns a list of upcoming arrivals with timing, origin, and status information.
AI agents call get_arrivals to retrieve information from NS Travel Information Server without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool performs a pure information retrieval operation querying train arrival data. It has no side effects, makes no modifications to data, executes no external commands, and poses minimal risk. The data returned is read-only public transit information. Appropriate for the Read category with low severity.
From the tool's definition Tool 'get_arrivals' retrieves real-time arrival information including platform numbers, delays, origin stations, and travel notes. The description explicitly indicates it 'returns' data with 'no mention of any write, execution, or destructive operations.'
Attacks that exploit this kind of access
Get real-time arrival information for trains at a specific station, including platform numbers, delays, origin stations, and any relevant travel notes. Returns a list of upcoming arrivals with timing, origin, and status information. It is categorised as a Read tool in the NS Travel Information Server MCP Server, which means it retrieves data without modifying state.
Register the NS Travel Information Server MCP server in PolicyLayer and add a rule for get_arrivals: 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 NS Travel Information Server. Nothing to install.
get_arrivals 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 get_arrivals 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 get_arrivals. 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.
get_arrivals is provided by the NS Travel Information Server MCP server (kallivdh/ns-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
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