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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive). The description adds substantial behavioral detail: default time window (±31 days), maximum 366-day window, duration range, workday limits via dayStart/dayEnd, and timezone handling. These details go well beyond annotations and clarify edge-case behavior.

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 and well-structured: it opens with the core purpose, then details parameters in a logical order, and ends with a timezone note. No filler or redundant phrasing.

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 presence of an output schema, the description covers all necessary invocation details: parameter defaults, constraints, workday limits, and timezone behavior. It provides complete context for an agent to call the tool correctly without missing critical information.

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 each parameter is already documented. The description largely restates these defaults and ranges, adding only a marginal note about slot bounds using the user timezone. It does not introduce significant new meaning beyond the schema, so the 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 clearly states the tool finds unoccupied time windows in the authenticated user calendar, using the verb 'find' with a specific resource. This distinguishes it from siblings like find_conflicts or get_event without ambiguity.

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 provides clear context for when to use the tool (to discover free time slots) and explains parameter usage with defaults and constraints, but it does not explicitly name alternative tools or state when not to use it. This is clear context without exclusion guidance.

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