Get live vehicle positions for one route from the agency GTFS Realtime vehicle positions feed. Pass agency to resolve the route inside one agency. Without agency the TTC is tried first and HSR second, so a route name that exists in both returns the TTC vehicles.
| Name | Required | Description | Default |
|---|---|---|---|
| limit | No | Maximum vehicles to return | |
| route | Yes | A route_id, short name, or long name, for example 501, King, or 1 | |
| agency | No | Optional agency the route belongs to: ttc or hsr |
Changes observed during successful MCP inspections.
Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
With no annotations present, the description carries the full burden, and it discloses a genuinely non-obvious behavior: the default agency resolution order (TTC first, HSR second) and the resulting collision outcome. It does not cover what happens when a route is not found, feed staleness, or return shape, which keeps it below a 5.
Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.
Is the description appropriately sized, front-loaded, and free of redundancy?
Two sentences, zero padding, front-loaded with the core action followed by the one caveat that matters. Every sentence earns its place.
Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.
Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?
For a simple three-parameter read query with full schema coverage, the description plus schema is enough to invoke it correctly. The main residual gap is the absence of an output schema combined with only a high-level mention of 'live vehicle positions', so the agent does not know what fields come back.
Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.
Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?
Schema coverage is 100%, so a 3 is the baseline, but the description adds real meaning beyond the schema's terse 'Optional agency the route belongs to' by explaining the fallback resolution order and its consequences. The route and limit parameters are left to the schema.
Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.
Does the description clearly state what the tool does and how it differs from similar tools?
The description names a specific verb and resource ('Get live vehicle positions for one route') and names its data source (agency GTFS Realtime vehicle positions feed). It is clearly distinguishable from siblings like next_departures, search_stops, and service_alerts without opening any schema.
Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.
Does the description explain when to use this tool, when not to, or what alternatives exist?
It gives concrete usage context for the optional agency parameter: pass it to resolve a route within one agency, omit it and the TTC is tried before HSR. That tells the agent how the call behaves in the ambiguous case. It stops short of stating when to prefer this over next_departures or service_alerts for related questions.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.
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