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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds that it returns full detail and accepts multiple identifier types, which is useful. However, it doesn't disclose behavior like error handling, whether the slug must be URL-encoded, or whether the response is paginated (unlikely for a single book). With annotations covering safety, a 3 is appropriate.

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, no filler. The first sentence front-loads the return content, and the second clarifies accepted identifier types. Every word earns its place.

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 simple single-parameter read tool with annotations covering safety and no output schema, the description is nearly complete. It could mention that the response is a single book object (not a list), but that's strongly implied by 'Full detail for one book'. The only minor gap is not stating what happens if the id is invalid, but that's not essential for a read-only lookup.

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 description coverage is 100%, so the schema already documents the 'id' parameter as 'A Siftivo work id, edition id, or URL slug'. The description repeats this by saying 'Accepts a work id, an edition id, or a slug', adding no new meaning beyond the schema. Baseline 3 is correct.

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 ('get') and resource ('book'), and enumerates the exact content returned: synopsis, authors, series position, genres, and the siftivo.com page. It also distinguishes itself from siblings by clarifying it accepts a work id, edition id, or slug, which is a clear scope statement.

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 implies when to use this tool: when you need full detail for one book and have an id or slug. It doesn't explicitly name alternatives or exclusions, but the sibling list includes get_my_book and search_books, and the description's focus on 'full detail for one book' provides clear context. It lacks an explicit 'use X instead when...' statement, so not a 5.

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