List authors

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

Annotations already mark the tool as read-only (readOnlyHint=true), so the description does not need to restate that. The description adds that the output includes each author's number of books, which is useful but does not disclose other behavioral aspects like pagination, ordering, or potential errors. With annotations covering safety, a score of 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?

The description is two sentences with no superfluous text. The first sentence states the core purpose, and the second gives actionable usage guidance. It is perfectly front-loaded and 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?

Given the tool's simplicity (two parameters, no output schema), the description covers the essential purpose and usage. It mentions the return value (authors with count) and directs to the sibling for a related task. While it could mention details like pagination or the output structure more explicitly, it is sufficiently complete for a straightforward list 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?

Schema description coverage is 100%, meaning both parameters (library_id and detail) are already documented in the schema. The description does not add new parameter-level information beyond reinforcing the library_id's role. The baseline of 3 applies.

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 clearly states the tool lists all authors of a book library with the number of books they have. It uses a specific verb-resource combination ('lists authors') and distinguishes itself from the sibling tool list_library_items by explicitly indicating that list_library_items is for listing books of a single author.

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 provides explicit guidance on when to use this tool (list all authors) and when to use an alternative (list_library_items for books of a specific author), including the exact filter parameters required. This helps the agent choose correctly.

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