mbta_routes

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

Annotations already declare readOnlyHint=true, so the safe read-only behavior is known. The description adds no further behavioral context such as response format, pagination, or rate limits, but it does not contradict annotations. Given the simple read-only nature, this is adequate but minimal.

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 extremely concise, using two sentences to convey the core action and optional filtering. It is front-loaded with the main purpose and every part adds value without redundancy or fluff.

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 filtered-list tool with full schema coverage and a readOnlyHint annotation, the description provides enough context to use it correctly. It does not specify return fields or pagination behavior, but the schema covers the limit parameter, and the tool's purpose is straightforward.

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%, meaning the schema already documents both 'type' and 'limit' parameters. The description repeats the type mapping already present in the schema and adds no new semantic information beyond what the schema provides.

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 uses a specific verb 'List' with a clearly defined resource 'MBTA (Boston) transit routes' and mentions optional type filtering. It distinguishes the tool from sibling tools like mbta_predictions and mbta_alerts by explicitly focusing on routes.

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 clearly indicates this tool is for listing MBTA routes and supports filtering by route type, providing clear usage context. However, it does not explicitly mention alternative tools for related data (like predictions or alerts) or state when not to use this tool, so it misses explicit exclusions.

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