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

Annotations already cover readOnly/idempotent safety, and the description adds meaningful context beyond them: the comparison windows are personal 30-day and 90-day rolling baselines, and the return includes the raw value plus contextual framing. It omits an important edge case – what happens when the user has less than 30/90 days of history.

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 operation, then usage triggers, then output framing. No redundant or filler text.

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 carries the burden of explaining returns, and it does so at a high level (value plus personal context). It leaves the concrete response shape and insufficient-history behavior unstated, which is a minor but real 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% and the schema already documents the metric enum, its upstream sources, and the local-date format. The description adds only the notion that the date is a 'single day' being compared, so baseline 3 is appropriate.

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?

Names a specific verb and resource (compare a single day's metric to 30/90-day rolling baselines) and implicitly distinguishes itself from absolute-value siblings like get_daily_summary or find_anomalies by framing results as personal-relative. An agent can identify the tool's role without opening the 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 explicit trigger phrasings: 'is this normal for me?' and 'how does today compare to my usual?'. It does not name an alternative tool or state when not to use it (e.g., instead of find_anomalies), so it stops short of full routing guidance.

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