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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so safety and determinism are covered structurally. The description adds genuine domain behavior beyond that — the fixed six-book catalog and the fact that transactions happen off-server — which is exactly the kind of context annotations cannot express.

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?

The purpose and return fields are front-loaded in the first sentence, with the slug enumeration and the Amazon caveat following in short order. The slug list restates the enum verbatim, which is minor redundancy, but nothing else is wasted.

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 single-parameter read tool with an output schema and full annotations, the description covers what it returns, which keys are valid, and the off-server purchase boundary. The base fields are technically redundant with the output schema, but nothing an agent needs in order to call it correctly is missing.

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% and the enum already spells out each slug with its full book title, so the description's slug list is largely duplicative. It adds no format or validation detail beyond the schema, making the baseline 3 appropriate.

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 — retrieve the details of one of J.A. Watte's six books by slug — and enumerates the fields returned (title, subtitle, page count, format, list price, Amazon link, site, description). An agent can distinguish this from sibling tools like recommend_book or search_blog immediately.

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 clear context: this is a lookup keyed by one of six known slugs, and adds an explicit exclusion that the books are sold on Amazon rather than through this server, which stops an agent from attempting a purchase flow. It does not, however, route the agent between this tool and sibling recommend_book, so the alternative-selection guidance is incomplete.

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