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

Annotations already establish readOnlyHint=true and openWorldHint=false, so the read-only, closed-world profile is covered. The description adds the key behavioral fact that the output is a set of genre slugs consumable by discover_titles, but says nothing about ordering, format, or completeness of the list.

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?

A single eight-word sentence that front-loads the essential fact with no filler. Nothing could be removed without losing information.

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 describe the return value, and it does: a collection of genre slugs. That is the critical missing piece for a zero-parameter enumeration tool, though it could note whether the list is stable or exhaustive.

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 tool takes zero parameters, so the schema has nothing to document and the baseline is 4. There are no argument semantics the description could usefully add.

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 names a concrete resource (the genre slugs) and ties it to the sibling tool that consumes them (discover_titles). The verb 'list' is only implied by the name, but an agent can immediately tell this is an enumeration tool distinct from discover_titles itself.

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?

Calling out that these are the slugs 'accepted by discover_titles' strongly implies the use case: fetch these before filtering with discover_titles. However, it never states the when/when-not conditions or a prerequisite chain explicitly, so usage must be inferred.

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