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

Annotations already declare readOnlyHint and openWorldHint, so safety is covered. The description adds real context beyond them: the returned sections are 'stable editorial' (not personalized), and personalized feeds plus streaming URLs are out of scope, which tells the agent what it will and won't get.

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 sentences, zero filler, with the primary scope stated first and the sibling routing second. Nothing redundant with the schema or annotations.

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?

An output schema exists so return values need no explanation, and the description covers scope plus the nearest alternatives. For a single-param read tool this is essentially complete, though it could note sibling differentiation against other bilibili feed tools.

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 category enum values are documented, so baseline is 3. The description adds slight value by framing category as a single 'vertical' choice among documentary/movie/TV/variety, reinforcing the one-vertical constraint.

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 (fetch) and resource (stable editorial sections) scoped to named Bilibili verticals, and explicitly names the sibling tools (bilibili_anime_home, bilibili_guochuang_home) it is not for. An agent can distinguish it from sibling home tools without opening any 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?

Gives explicit exclusions ('personalized feeds and streaming URLs are excluded') and routes anime queries to named alternatives, which is strong guidance. It doesn't address other bilibili siblings like bilibili_popular or bilibili_ranking, so it stops short of fully disambiguating.

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