Real-time arrivals and departures at a stop. Returns predicted arrival times, schedule deviation (how many seconds late/early), vehicle positions, and any active service alerts. The predicted boolean on each arrival indicates whether GPS tracking backs the estimate — predicted=false means schedul...
Part of the Onebusaway Mcp Server server.
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AI agents call onebusaway_get_arrivals to retrieve information from Onebusaway Mcp Server without modifying any data. This is common in research, monitoring, and reporting workflows where the agent needs context before taking action. Because read operations don't change state, they are generally safe to allow without restrictions -- but you may still want rate limits to control API costs.
Even though onebusaway_get_arrivals only reads data, uncontrolled read access can leak sensitive information or rack up API costs. An agent caught in a retry loop could make thousands of calls per minute. A rate limit gives you a safety net without blocking legitimate use.
Read-only tools are safe to allow by default. No rate limit needed unless you want to control costs.
{
"version": "1",
"default": "deny",
"tools": {
"onebusaway_get_arrivals": {}
}
}See the full Onebusaway Mcp Server policy for all 15 tools.
These attack patterns abuse exactly the kind of access onebusaway_get_arrivals gives an agent. Each links to the full case and the policy that stops it:
Other read tools across the catalogue. The same approach applies to each: allow, with a rate cap to control cost.
Real-time arrivals and departures at a stop. Returns predicted arrival times, schedule deviation (how many seconds late/early), vehicle positions, and any active service alerts. The predicted boolean on each arrival indicates whether GPS tracking backs the estimate — predicted=false means schedule-only. Use tripId from results for follow-up onebusaway_get_trip calls. Stop IDs use agency-prefixed format: {agencyId}_{localId} (e.g. "1_75403").. It is categorised as a Read tool in the Onebusaway Mcp Server MCP Server, which means it retrieves data without modifying state.
Register the Onebusaway Mcp Server MCP server in PolicyLayer and add a rule for onebusaway_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 Onebusaway Mcp Server. Nothing to install.
onebusaway_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 onebusaway_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 onebusaway_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.
onebusaway_get_arrivals is provided by the Onebusaway Mcp Server MCP server (@cyanheads/onebusaway-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 15 Onebusaway Mcp Server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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