library_lookup

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

With no annotations, the description carries the full behavioral burden and does well: it discloses fuzzy matching ('写错一两个字也找得到'), the domain exclusion for lyrics, and a best-effort 'if not found, search elsewhere' workflow. It stops short of describing what a hit looks like (snippet, source book, match count) beyond the k limit, which is a minor gap for a no-annotation tool.

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?

Four sentences, front-loaded with the core lookup purpose and followed by capability, exclusion, and fallback. Slightly redundant tail ('歌词不收… 歌词可以另外查') could be trimmed, but every element earns its place and nothing is buried.

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 2-parameter read-lookup with no annotations and no output schema, the description adequately covers purpose, input tolerance, exclusions, and the cross-tool workflow. The one hole is return behavior, which the absent output schema means the description could have explained.

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 both 'query' and 'k' are already documented in the schema. The description reinforces query flexibility ('可以只给半句'), which adds a little meaning beyond the schema's '想查的词或句子', but leaves k entirely to the schema. Baseline 3 is appropriate when the schema does the heavy lifting.

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?

The description states a specific verb ('查' look up) and resource ('梗、一句话或半句话' in the library's reference books), and gives a concrete example of the use case (unfamiliar internet slang). It also distinguishes this tool from the sibling library_save and from a separate lyrics lookup, so an agent can tell what it is and is not without opening a 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?

Explicit when-to-use (someone said something you didn't understand), what input is accepted (half a sentence, typos tolerated), an exclusion (lyrics are not accepted, with a stated exception), and a fallback workflow (search elsewhere, understand, then save with library_save). This is a full routing guide naming the sibling tool.

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