compare_periods

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

With no annotations provided, the description carries the full burden. It states the tool returns a 'side-by-side comparison with percentage changes,' implying read-only behavior, but it does not explicitly confirm non-destructiveness or disclose any other behavioral traits like authentication needs or rate limits. The description is adequate but not explicit.

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 two sentences, front-loaded with the core purpose and followed by concrete examples. Every sentence adds value, and there is no wasted 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?

Given the lack of an output schema, the description adequately explains the return format ('side-by-side comparison with percentage changes'). It covers the 5 parameters implicitly through schema coverage. For a comparison tool with moderate complexity, this is fairly complete, though it could mention default behavior for the metrics parameter.

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%, so the input schema already provides clear descriptions for all parameters (date strings and metrics array). The tool description adds no additional meaning beyond the schema's parameter info, so a baseline of 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?

The description uses a specific verb ('Compare') and clearly identifies the resource ('health metrics between two time periods'). It provides concrete examples ('How did I sleep this week vs last week?') and distinguishes from sibling tools like 'compare_conditions' by focusing on time period comparison rather than condition comparison.

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?

The description includes explicit usage examples that guide the agent on when to use the tool (comparisons like week-vs-week or month-vs-month). However, it does not mention when not to use it or list alternative tools for related queries, which would improve guidance.

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