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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description adds real behavioral context beyond them: the tool requires authentication and points the agent at the error text returned when not signed in. It still omits return/pagination behavior, but the auth disclosure is meaningful added value.

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 tight sentences with the resource scoping front-loaded and no filler. The auth note is a slight detour but still earns its place by telling the agent what a failure looks like.

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 read-only, no-output-schema list tool with three optional parameters, the description covers what is returned and the sign-in requirement, but leaves limit/pagination and the media_type filter unexplained despite low schema coverage. Adequate but with a clear gap.

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 only 33% (status is documented; limit and media_type are not). The description's phrasing ('watching or reading', 'plan to', 'finished') loosely maps to the media_type and status enums but gives no detail on limit or how results are bounded/paginated, so it only partially compensates for the coverage gap.

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 resource (the signed-in person's AnimeHunt library) and enumerates its contents — watching/reading, planning, finished, with scores and progress — which effectively conveys a read of the user's own collection. It is distinguishable from siblings like add_to_library or search_titles, though it never names an explicit verb and relies on the reader to infer 'retrieve/list'.

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 prerequisite (must be signed in) is stated clearly, which is genuinely useful routing information, but there is no guidance on when to choose this over alternatives such as discover_titles, search_titles, or recommend_from_liked. Usage is only implied by the description of the library contents.

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