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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint, so the safety profile is covered structurally. The description adds only the single-day scoping constraint and none of the useful behavioral context an agent might want here — e.g. that Oura attributes data to the day of wake-up, which the schema notes but the description does not, nor how it differs from get_last_night_sleep or get_morning_briefing.

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?

Three short sentences: what it returns, when to use it, and where to go otherwise. Zero filler and the purpose is front-loaded ahead of the routing hint.

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 no output schema, the description does tell the agent which three score families come back, and the scopes parameter lets it narrow the set. It stops short of describing the return shape or how a partial scopes selection affects the response, which slightly limits completeness.

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% and the date parameter already carries the important local-vs-UTC guidance. The description adds no parameter-level detail beyond implying a single-date scope, so the baseline 3 applies.

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 and resource ('Get a single-day summary of Oura Ring data') and enumerates the domains covered (sleep, readiness, activity). It explicitly separates itself from get_date_range, so an agent can choose between them 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?

Gives a concrete trigger ('how was my [day]', snapshot of one specific date) plus an explicit exclusion routing range queries to get_date_range. Both the when and the when-not are stated.

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