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

Annotations already declare readOnlyHint=true, openWorldHint=false, and destructiveHint=false, so the safety profile is covered. The description adds behavior the annotations do not: what a result contains (a one-paragraph summary and a slug for get_grammar_point), which is real chaining information. It does not mention pagination or result caps, so it falls short of a 5.

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 tight sentences, front-loaded with scope and filter modes, then return shape and handoff, then the exclusion. Every clause, including the vocabulary-tool warning, earns its place with no redundancy.

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?

With no output schema, the description carries the return-value burden and does it (summary paragraph plus slug). A zero-required-parameter search tool is fully specified: scope, filter modes, keyword vocabulary, output shape, and the sibling to call next.

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 the baseline is 3, but the description goes beyond the schema by enumerating what qualifies as a keyword: English (comparison, passive), a Chinese marker (把, 了), or a term name. That is genuinely additive, though it does not elaborate on the level parameter beyond the schema's own wording.

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 (Search) and resource (195 Mandarin grammar points) plus the two filtering axes (keyword, HSK level, or both). It explicitly names the sibling get_grammar_point and the handoff artifact (the slug), so the agent can distinguish it from lookup/search 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 an affirmative trigger ("Use this to find which grammar point covers a pattern") and an explicit exclusion ("Do not use it for vocabulary questions"), and routes the agent onward to get_grammar_point via the returned slug. This is the when/when-not/alternative pattern in full.

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