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

Annotations already declare readOnlyHint=true, destructiveHint=false, openWorldHint=false, so the safety profile is covered. The description adds genuine behavioral context the annotations cannot: the result is ordered pedagogically rather than sorted, and each entry is a themed group carrying pinyin and meaning. It stops short of saying how many lessons are returned or whether the set is capped/paginated.

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 sentences, each with a distinct job: what it returns, what kind of ordering it is, and when to use or avoid it. No filler, no restatement of the title, and the routing constraint comes last where it is easy to find.

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 burden of describing the return shape, and it does so reasonably ('themed group of words with pinyin and meaning'). For a one-parameter, low-complexity read tool this is nearly sufficient; the only omitted detail is the volume/limit of lessons the caller should expect.

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 single parameter already documents 'HSK level, 1 to 5' with min/max bounds. The description only restates the same 1-to-5 range, adding no format, default, or edge-case semantics beyond the schema. Baseline 3 applies when the schema does all the work.

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 (get the opening vocabulary lessons of an HSK level) plus the organizing principle (GraphChinese teaching order, themed groups with pinyin and meaning). It explicitly negates a common misreading — 'a learning order, not an alphabetical word list' — so an agent can separate it from search_dictionary and get_topic_words 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 explicit when-to-use ('user asks what words to learn first, or what to start with at HSK 1 to 5') and an explicit when-not-to-use with the named alternative ('Do not use it to look up one word (use lookup_word)'). This is the strongest form: trigger condition plus routing exclusion.

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