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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered; the description adds genuinely new behavior: the exact field scope returned, that relationships are publication-filtered, and that unpublished and unknown IDs both yield not found (no existence leak). It does not discuss response size, link lifetimes, or rate limits, keeping it below the top mark.

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 tight sentences, front-loaded with the action and scope, followed by return shape and error behavior. The closing sentence about content being "deliberately public sample links" is slightly dense and reads as a data-policy note, but it is not filler.

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?

No output schema exists, so the description must sketch the return value, and it does: public REST detail fields, publication-filtered relationships, and public page/media links, plus the not-found case. The phrase "public REST detail fields" remains undefined for an agent that cannot see the REST spec, which is the main residual gap for a single-parameter fetch tool.

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?

With one parameter at 0% schema description coverage, the description must carry the load: it identifies the argument as a catalog ID sourced from search_books or a related record, which is useful provenance. However, it does not mention the numeric string format enforced by the pattern (^[1-9][0-9]{0,18}$) or the 19-character limit, so an agent could still pass a malformed ID.

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 one published book by its catalog ID") and immediately separates itself from search_books by noting the ID is obtained from that tool. The scope qualifier "published" also distinguishes it from a raw lookup of any record.

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 a clear routing rule: this tool takes an ID that came from search_books or a related record, which implicitly tells the agent to search first and fetch second. It does not explicitly state the inverse ("do not use this to search by title"), so it stops short of full when/when-not guidance.

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