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

Annotations already declare readOnlyHint, openWorldHint, and non-destructive, so safety is covered. The description adds the underlying GET endpoint and the conditional return behavior of expand_products, but says nothing about errors for unknown ids or the response shape.

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?

Two compact clauses with zero filler, and the primary behavior (single category by id) is front-loaded before the optional expansion. Fragment style but appropriately terse for a simple getter.

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 read-only two-parameter tool with full schema coverage and no output schema, the description covers purpose and the expand_products conditional. Only minor gaps remain (error cases, return shape), which are acceptable at this complexity.

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%, so both parameters are already documented with examples and patterns. The description restates the id format and the expand_products effect but adds no syntax or edge-case detail beyond the schema. Baseline 3 applies.

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?

States a specific verb/resource: retrieves one category by id, with the id prefix format (cat_...) and the optional product expansion. It distinguishes itself from list_categories by explicitly saying 'One category by id', though it doesn't name that sibling.

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 implied: use this for a single known-id lookup rather than listing. There's no explicit when-to-use/when-not, no mention of choosing list_categories when the id is unknown, and no prerequisite notes.

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