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

Annotations already declare readOnlyHint, openWorldHint, and idempotentHint, covering the safety and determinism profile. The description adds value by specifying the content of the response (bio, dates, photo IDs, identifiers) and the input preprocessing (stripping a leading '/authors/' prefix), which are behavioral traits not captured in annotations. It does not mention error handling or rate limits, but with annotations covering the safety profile, a 4 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 filler. The main purpose and return content are front-loaded in the first sentence, and the usage guidance is a single clear sentence. Every word earns its place, making it appropriately concise and well-structured.

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-only tool with an output schema available and annotations covering safety, the description is complete. It states what the tool does, what it returns, and how to obtain the required input (via search_authors). No essential information is missing for an agent to call this tool correctly.

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 already fully documents the single parameter author_id, including format (OL…A) and prefix stripping. The description repeats this information without adding new semantic detail, so it does not compensate beyond the schema. With schema coverage at 100%, the baseline of 3 is correct.

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 uses the specific verb 'Fetch' with a clear resource 'author detail' and scope 'by Open Library Author ID'. It lists what is returned (bio, dates, photo IDs, linked identifiers) which distinguishes it from siblings like get_author_works or get_work, and it explicitly points to search_authors as the precursor tool.

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 a clear workflow: use openlibrary_search_authors to find an author ID first. This provides contextual guidance. However, it does not explicitly state when not to use this tool versus siblings such as get_author_works, so it lacks exclusions, making it a strong but not perfect usage guideline.

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