compare_periods

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

With read-only, idempotent annotations already covering the safety profile, the description usefully adds that results are informational rather than medical advice and that missing fields are reported as 'not recorded' rather than zero. This is valuable behavioral context beyond the annotations, though it says little about response shape beyond what the output schema provides.

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 description is dense and front-loads the comparison purpose, example, and metric coverage. It is somewhat long and begins with a stray 'I2.' artifact, but otherwise every sentence adds useful 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?

Given the output schema, the description does not need to explain return fields in full, and it adequately covers the comparison semantics, metric scope, and missing-data handling. It is nearly complete, with only sibling differentiation and deeper usage exclusions left unaddressed.

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 dates and metrics are already documented. The description still adds the meaningful per-period limit of 366 days and summarizes the metric categories and comparison outputs, giving useful context beyond the schema.

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 operation and resource: compare two periods across health and activity metrics, with example usage. It is clear on its own, though it does not explicitly distinguish itself from siblings such as trend or weekly_review.

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 concrete use case (this October vs last October) and a hard constraint that each period can be up to 366 days. It does not state when to prefer an alternative sibling or when not to use the tool, so the routing guidance is clear but incomplete.

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