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 genuinely useful behavioral constraints beyond that: minute samples are ten minutes apart and source history is capped at seven days, which tells the agent what queries will fail or be sparse. These facts are partially echoed in the schema's parameter text, which keeps it from a 5.

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 sentences, zero filler. The core identity and the metric variants come first, and the retention/granularity caveats follow in a single compact clause.

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 an output schema, full parameter coverage, and annotations in place, the description only needs to supply domain constraints and valid values — which it does. The one remaining gap is default time-range behavior when from/to are omitted.

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 description coverage is 100%, so the baseline is 3, but the description earns more by enumerating the concrete allowed values for 'metric' — the schema only says 'Required source metric path variant' with no enum, so the description is the sole source of that constrained vocabulary. It does not clarify from/to defaults or behavior when the range is omitted.

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 ('Returns') and a specific resource ('one aggregate Fortnite metric path'), and enumerates the two valid metric paths (in-client-peak-ccu, in-match-peak-ccu) plus the bucket granularities. The word 'one' implicitly distinguishes it from the plural sibling fortnite_ecosystem_metrics, but that contrast is never made explicit.

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?

Usage is implied rather than stated: 'returns one aggregate metric path' suggests the plural sibling should be used for multiple metrics, but no alternative is named and no when-not condition is given. An agent can infer the routing but must do the work itself.

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