md_transit_trip_updates

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true, so the description doesn't need to restate safety. It adds useful behavioral context: the API key requirement and the meaning of each agency enum value. It does not detail response format or rate limits, but for a read-only data-fetch tool with a single parameter, this is acceptable.

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 two sentences. The first sentence states the purpose; the second delivers the API key requirement and the full agency mapping. No filler or redundancy.

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 tool with one parameter and no output schema, the description covers the essential aspects: what it does (real-time delays/cancellations), the required credential, and the valid agency identifiers. It is self-contained enough for an agent to invoke correctly without additional context.

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?

The schema only says the agency is a 'Swiftly agency key'. The description enriches this by mapping each enum value to a human-readable service (e.g., 'mta-maryland' = Local Bus). This greatly improves the agent's ability to pick the correct parameter value beyond the raw 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 clearly states the verb 'Get' and the resource 'real-time trip updates (delays, cancellations) for Maryland MTA transit', which is specific and distinguishes this tool from transit tools for other agencies or different data types like vehicles or alerts. It also enumerates the exact agency keys with friendly names.

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 description provides clear context: use for delays and cancellations on Maryland MTA services. It also mentions a prerequisite (SWIFTLY_API_KEY) and lists the four agency options. However, it does not explicitly name alternative tools or when not to use this tool, but the context is strong enough for selection.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.