Find public transit routes for a city, with optional search by name or number.
Lists public transit routes/lines for a supported city with optional search filtering.
| Name | Required | Description | Default |
|---|---|---|---|
| city | Yes | City identifier or alias (e.g. 'msp', 'boston', 'sf_bart', 'chicago', 'portland') | |
| query | No | Optional search query (e.g. 'Red', 'Blue', 'Green', '66') |
Changes observed during successful MCP inspections.
v1.0.0Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?
No annotations are provided, so the description carries behavioral burden. It discloses that the tool lists routes and supports optional search filtering, but it does not explain behavior such as whether an unsupported city produces an error, how search filtering matches (substring vs exact), or what the response includes. This is acceptable for a simple read-only listing tool but not richly transparent.
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?
The description is a single, front-loaded sentence with no redundant wording. Every element — action, resource, scope, and filtering capability — 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 low-complexity tool with two parameters and no output schema, the description provides enough to invoke it correctly: it lists routes for a city with optional search filtering. It could be slightly more complete by pointing to list_supported_cities for valid city identifiers or clarifying search matching, but these are minor gaps.
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 description coverage is 100%, so the schema already documents both city and query parameters. The description adds only a generic reference to 'optional search filtering,' which adds no substantive meaning beyond the schema. The baseline of 3 applies because the schema carries the parameter documentation burden.
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 ('Lists'), a specific resource ('public transit routes/lines'), and a scope ('for a supported city'). It also mentions optional search filtering, making the tool's function clear. The resource type distinguishes it from sibling tools that deal with stops, departures, and service alerts.
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?
The phrase 'for a supported city' implies the caller should know whether a city is supported, but it does not explicitly point to list_supported_cities as the way to discover valid identifiers. No explicit when-to-use or when-not-to-use guidance is provided, though the intended use is reasonably inferable from the description.
Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.