mbta_get_historical_assignments

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

No annotations are present, and the description only states the tool 'shows' data, implying a read operation. It does not disclose potential side effects, data source nuances, or limitations like rate limits or data freshness, which are crucial for a historical data endpoint.

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, direct sentence without redundancy. It is appropriately concise, though adding a bit more structure (e.g., bullet points or examples) could improve clarity without sacrificing brevity.

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?

Given the lack of output schema and only three parameters, the description is minimal. It does not specify the return format, error handling, or data range constraints (e.g., maximum 'days' allowed), leaving the agent with gaps for correct invocation.

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 baseline is 3. The description does not add extra meaning beyond the schema; for example, it does not clarify station_id format or the 'days' parameter boundaries, but the schema already provides adequate definitions.

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 tool retrieves historical track assignments using the IMT API, which distinguishes it from real-time or predictive tools among siblings. However, it could more explicitly contrast with similar history retrieval tools if any exist.

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?

No guidance is provided on when to use this tool versus alternatives like predictions or schedules. The description lacks any mention of preferred contexts or exclusions.

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