Week summary

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

Annotations already declare readOnly/openWorld/idempotent, but the description adds cost telemetry ('three Garmin requests per day plus one for the activities, over 20 in all'), an explicit throttling warning, a 50-activity cap, and a non-obvious data convention ('a night's sleep belongs to the day it ended on') that materially affects interpretation.

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?

Purpose and scope are front-loaded in the first sentence, followed by routing, then cost caveats. Every sentence carries actionable information with no filler, despite the density.

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?

An output schema exists, so return-shape explanation is unnecessary; the description instead covers the things structure can't: sibling routing, request cost, call-frequency limits, and the sleep-day attribution rule. Nothing an agent needs to invoke this 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?

Schema coverage is 100% and the sole parameter is fully documented, so the baseline is 3. The description adds genuine meaning beyond the schema by specifying that the default 'today' is evaluated in the account's timezone and clarifying end_day as the last day of the seven-day window.

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 ('Summarise') and resource (the seven days ending on end_day), then enumerates exactly what is returned: steps, resting heart rate, sleep hours, morning readiness, and activities (up to 50). This is instantly distinguishable from day- and trend-level siblings.

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?

Explicitly routes the agent: get_day_summary for one day in full, get_trend for a single metric over longer ranges, and a hard caution not to call week_summary repeatedly because of its request cost. When-to-use, when-not-to-use, and alternatives are all named.

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