list_subjects

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

Annotations already declare readOnlyHint=true and openWorldHint=true, so safety is covered. The description adds the sort order (largest first) and a handoff to search_titles, but says nothing about result size, truncation, or how media_type narrows output.

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 tight sentences, zero filler, and the core resource plus ordering is front-loaded. No restructuring needed.

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?

An output schema exists so return shape is covered, and the tool has no required parameters. However, for a tool that supports media_type filtering and multi-library selection, the description omits anything an agent would need to pick parameters 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?

Schema coverage is only 50% — media_type has no schema description at all — and the description never mentions either parameter. It does not compensate for the gap, leaving the filtering behavior of media_type and the library default undocumented anywhere.

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 the resource clearly ('Subjects (genres) in a library's collection') plus a meaningful ordering ('largest first'). The listing verb is implied rather than stated, and no sibling is named as an alternative, so it falls short of a 5.

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?

'Use the ids with search_titles' gives a downstream workflow hint, which is useful. But it does not say when to call this versus calling search_titles directly, nor any conditions or prerequisites for its own use.

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