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

Annotations already declare readOnlyHint=true, idempotentHint=true, and openWorldHint=true, so safety behavior is covered. The description adds meaningful behavioral context beyond annotations: a 30-day lookback window and the fact that measurements may be sparse due to how Oura computes VO2 max.

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, front-loaded with the core action and immediately followed by the key caveat and input format. No wasted words; every sentence earns its place.

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?

For a single-parameter, read-only lookup with annotations covering safety, the description is nearly complete: it explains the window, sparsity, and date format. The only minor gap is not stating what is returned when no measurement exists, but no output schema is present and the core behavior is clear.

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 sole parameter is fully documented in the schema with the YYYY-MM-DD pattern and local-date requirement. The description reinforces the local-date and strict format requirement but adds no syntax or interpretation beyond what the schema already provides, 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?

The description states a specific verb and resource: 'Get the most recent VO2 max measurement within 30 days of the queried date.' It is clear what the tool does, but it does not differentiate from related siblings like get_cardio_age, which could also cover fitness metrics.

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 — use this tool when you need a VO2 max value near a given date. The description adds useful context that measurements may be sparse because they come from outdoor walks/runs, but it never explicitly states when to choose this over alternatives or what to do if no measurement exists.

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