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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered; the description adds the operational consequence ("its server marks it read-only, so it runs straight away") which tells the agent no approval round-trip is needed. It also spells out the returned field set, valuable since no output schema exists. It does not cover failure behavior for a nonexistent ID.

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?

Three short sentences, front-loaded with purpose, then return shape, then the sibling escape hatch. Every sentence earns its place and nothing is repeated.

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 two-parameter read tool with no output schema, the description supplies the missing return shape, the sibling routing, and the execution model. Nothing an agent needs to invoke it correctly is absent.

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 both parameters carry descriptions (`site_id` with its enum and URL, `category_id` with its meaning), so the schema does the heavy lifting. The description adds only the phrase "by ID", which is already implied by the required integer parameter; 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 and resource ("Gets a single WordPress category by ID") and immediately contrasts with the sibling `wp_list_categories` for the children case. An agent can distinguish it from the many list/term tools without opening the schema.

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?

Explicitly names the alternative for a related need: "To get children, call `wp_list_categories` with `parent` = this ID." Missing is guidance on the inverse case (when to use `wp_list_categories` to discover an ID in the first place) or what happens if the ID is unknown, but the routing context is clear.

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