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

Annotations already cover the safety profile (readOnly, non-destructive, closed-world), so the description's added value is limited to disclosing that the response bundles related categories. It says nothing about what happens with an unknown slug, error behavior, or response shape beyond the vague "in full".

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?

A single tight sentence with no filler, front-loading the resource and the lookup key. It is arguably too terse for a tool with no output schema, but nothing is wasted.

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 single-parameter read tool with annotations covering safety and a fully documented schema, the basics are covered. With no output schema, however, the description gives only a one-clause sketch of the return value ("in full" plus related categories), leaving the agent to discover the actual payload structure.

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% and the slug property already carries concrete examples (school-bus, cutaway-bus, motorcoach). The description only restates "by slug" and adds no format, casing, or lookup semantics beyond 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?

"One bus category in full, by slug" states a specific verb (retrieve) and resource, and the singular framing implicitly contrasts with the sibling list_bus_categories. It stops short of naming the sibling outright, so an agent must infer the distinction.

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?

Usage is only implied: "one ... by slug" suggests detail lookup versus listing, and "related categories worth considering instead" hints at a comparison/exploration workflow. There is no explicit when-to-use, when-not-to-use, or named alternative such as list_bus_categories or search_buses.

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