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

Annotations already declare this is read-only, idempotent, and non-destructive, so the safety burden is light. The description adds useful behavioral detail beyond annotations: it returns the days remaining and unlock moments for New Zealand, the UK, and the US East Coast, and the timezone parameter yields that zone's local-midnight unlock.

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?

The usage trigger is front-loaded, followed immediately by what is returned and the optional parameter's effect. There is no filler; both sentences carry distinct 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 an output schema present, return structure needn't be described in detail. For a simple read-only countdown tool with one optional parameter, the description covers trigger, scope, returned facts, and the timezone effect, leaving no material gap.

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 100%, so the baseline is 3, but the description adds real meaning: the timezone parameter is not just an IANA zone but specifically selects that zone's local-midnight unlock. That clarifies the semantic effect of the optional parameter beyond the schema's example string.

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 specific resource and gives a concrete verb-like retrieval ('returns the confirmed release date... days left... unlock moments'), so an agent knows exactly what it fetches. It lacks explicit differentiation from the overlapping sibling get_unlock_time, which keeps it below 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?

It gives a clear triggering condition: 'Use this when someone asks how long until GTA 6 launches.' That is a strong positive usage cue, but it offers no when-not guidance and does not route the agent away from or toward get_unlock_time for unlock-time-specific queries.

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