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

Annotations already declare readOnlyHint and openWorldHint, so the safety profile is covered and the description's added burden is scope, not safety. The description does add one real behavioral fact: it returns the authoritative accepted values, and genre values are deliberately excluded because they are 'separately maintained' elsewhere. That is useful scope disclosure but thin for an open-world API-reading tool.

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, both front-loaded with the essential information and zero filler. The sibling redirect is compactly appended rather than buried in prose.

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?

Because an output schema exists, the description need not explain return values, and with no parameters and covered safety annotations the remaining burden is small. It is nearly complete, though it could note that the returned intervals and metric values are the ones to pass into the Fortnite metric tools, closing the loop on how the output is consumed.

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?

Zero parameters, so there is nothing for the description to disambiguate and the baseline of 4 applies. The description correctly conveys that all selectivity happens through the returned value list rather than through input arguments.

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 a specific verb ('Lists') and a precise resource ('the exact intervals and metric values accepted by the Fortnite Data API'), which tells an agent exactly what content the tool returns. It also explicitly names the sibling it is not (fortnite_genres), so the boundary is unambiguous without opening either schema.

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?

Provides explicit routing for the adjacent case: use fortnite_genres for the live genre list. It stops short of stating the primary usage pattern (call this before/alongside fortnite_island_metric or fortnite_ecosystem_metric to discover valid values), so the trigger for using this tool itself is only implied rather than stated.

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