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

Annotations already declare readOnlyHint and openWorldHint, and the description adds real value on top: the list is 'complete' and 'live' (so no pagination or parameter filtering), and it draws a taxonomy boundary between genres and free-form island tags. It doesn't discuss freshness cadence or ordering, but the key behavioral facts are covered.

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 short sentences, zero waste, with the primary behavior stated first and the cross-tool usage note second. Nothing is repeated from the schema or annotations.

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 zero-parameter read-only enumeration with an output schema and safety annotations, the definition covers what it returns, how it fits with the sibling rankings tool, and the tags-vs-genres distinction. Nothing an agent needs to call it correctly is missing.

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 no parameters, so there is nothing to disambiguate and the baseline applies. The description correctly implies no filtering input is needed by calling the result 'complete'.

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?

Names a specific verb and resource ('Returns the complete live list of Epic Fortnite island genres') and scopes it as the full canonical list. It also distinguishes itself from the obvious sibling by framing itself as the producer of slugs consumed by fortnite_genre_rankings.

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?

Gives clear downstream context: take a returned slug into fortnite_genre_rankings, and don't confuse genres with island tags, which are a separate free-form field. It lacks an explicit 'call this first when you need to filter by genre' framing, but the implied workflow is easy to infer.

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