Summarise a period

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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is known. The description adds valuable behavioral context by detailing the return values (mean, std, median, min, max) and explaining days_missing as a coverage gap, not a record count. This goes beyond the annotations without contradicting them.

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 concise, front-loaded with the main purpose, and structured clearly. The Args section is formatted neatly, and every sentence adds value—no fluff or repetition.

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?

The tool is simple (2 params), and the description explains the return values and the meaning of days_missing. Given the annotations indicate a read-only, open-world operation and an output schema exists, the description is sufficiently complete for an agent to use the tool effectively.

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?

The input schema only provides parameter names and types (string). The description adds essential meaning: both are ISO 8601 dates and define the start/end of the range. With schema description coverage at 0%, this compensation is crucial for correct invocation and is done clearly.

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 opens with 'Summarise recovery, sleep and strain over a date range,' clearly stating a specific verb, resource, and scope. It distinguishes from sibling tools like list_recoveries and compare_periods by focusing on aggregation over a range rather than individual records or comparisons.

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 clearly implies its use case: when you need summary statistics over a date range. It doesn't explicitly state when not to use it or name alternatives, but the context is clear enough that an agent can infer it's for aggregation rather than raw data retrieval.

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