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

Annotations already declare readOnly, idempotent, non-destructive, and closed-world, so the bar is lower. The description still adds real value: the 50-item page cap and the explicit statement that book text is never returned, which tells the agent to fetch get_book or get_passage for content.

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 short sentences, no filler, with the core scope (whose books) front-loaded and the pagination and content-exclusion constraints immediately after.

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?

With no output schema, the description must say what comes back; it names the shape ('saved books with their reader addresses') and excludes book text, which is enough for an agent to know the payload. It could say more about ordering or pagination termination, but the essentials are present.

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% with per-parameter descriptions and an enum on status, so the schema already carries the semantics. The description's only added detail is the 50-item ceiling, which is already encoded as the limit maximum in the schema.

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 ('List the saved books of the signed-in member') and scopes it to the caller's own library, which implicitly separates it from search_books or browse_collection. It stops short of naming a sibling to route away from, so it is clear but not maximally differentiating.

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 this is the tool for the caller's personal saved books, but never states when to prefer it over search_books or browse_collection, nor any prerequisites or exclusions. The '5 at a time' pagination note is behavioral rather than usage guidance.

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