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

Annotations already convey that this is a mutating but non-destructive and idempotent operation. The description adds the useful detail that current_page updates reading progress, but it does not disclose partial-update behavior, required book_id semantics, or any other side effects beyond the annotation coverage.

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 description is a single, efficient sentence with no filler. It front-loads the action and resource, then immediately lists the mutable fields, making it easy to scan.

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 straightforward CRUD update tool with fully documented parameters and annotations covering the safety profile, the description is largely complete. It could explicitly mention that unspecified fields remain unchanged and what the tool returns, but no output schema exists and the core semantics are clear.

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?

The input schema has 100% description coverage, with every one of the 8 parameters documented. The description adds little beyond the schema, though it does frame current_page as 'reading progress,' which is a mild semantic enhancement. Baseline 3 is 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?

The description states a specific verb ('Update'), a clear resource ('a book'), and enumerates the exact fields that can be changed (status, rating, notes, current page). This makes it easy to distinguish from sibling tools like create_book, delete_book, and list_books.

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 clear context: this tool modifies existing book fields rather than creating or deleting a book. However, it does not explicitly state when not to use it or name alternative tools for related operations, so it stops short of full routing guidance.

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