22 tools. 1 can modify or destroy data without limits.
1 write tool that can modify data. Rate limits recommended.
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Write operations (mta_plan_trip) modify state. Without rate limits, an agent can make hundreds of changes in seconds — faster than any human can review or revert.
{
"mta_plan_trip": {
"limits": [
{
"counter": "mta_plan_trip_per_hour",
"window": "hour",
"max": 30,
"scope": "grant"
}
]
}
} Prevents bulk unintended modifications from agents caught in loops.
{
"bike_get_availability_summary": {
"limits": [
{
"counter": "bike_get_availability_summary_per_minute",
"window": "minute",
"max": 60,
"scope": "grant"
}
]
}
} Controls API costs and prevents retry loops from exhausting upstream rate limits.
The SubwayInfo NYC server has 1 write tools including mta_plan_trip. Set a rate limit in your policy -- for example, 10 calls per hour prevents an agent from making more than 10 modifications per hour. PolicyLayer enforces this at the gateway, before calls reach SubwayInfo NYC.
22 tools across 2 categories: Read, Write. 21 are read-only. 1 can modify, create, or delete data.
Register the SubwayInfo NYC MCP server in PolicyLayer, apply the suggested rules above (adjust the limits to your use case), and point your AI client at the PolicyLayer proxy URL instead of the server directly. Your agents keep the same tools; PolicyLayer evaluates every call against policy before it executes. Nothing to install, live in minutes.
Deterministic rules across all 22 SubwayInfo NYC tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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