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

Annotations already cover read-only, idempotence, and destructiveness. The description adds meaningful context: it operates on the signed-in reader's personal shelves, can combine status and rating in one call, and can update existing entries ('move it to a different shelf'). No contradiction with annotations.

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 with no filler: first states core capabilities, second gives required input provenance, third gives a concrete combined-field example. The most important information is front-loaded.

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 five-parameter mutation tool with no output schema, the description is complete: it covers the required id, optional state fields, and a composition example. It doesn't explain return values or error cases, but no output schema means that burden is lighter; a small gap is the lack of explicit guidance on removing books.

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 60%, leaving workId and readingStatus descriptions missing. The description compensates by explaining where workId comes from and illustrating readingStatus+rating usage ('Finished it, four stars'). The 'shelf' wording maps somewhat ambiguously to readingStatus, but the example clarifies it.

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 names concrete actions (put on shelf, move, rate, record progress) and the resource (signed-in reader's library), so a reader understands the tool's behavior. It doesn't explicitly differentiate from siblings like remove_from_library or get_my_library, but the mutation framing makes the distinction inferable.

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 description gives useful provenance guidance for workId ('from search_books, get_book, or recommend_from_titles'), but it never states when to use this tool versus remove_from_library or get_my_library. No exclusions or alternatives are named, so the agent has to infer the boundary.

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