Query free/busy times

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

Beyond the annotations (readOnlyHint, idempotentHint), the description adds important behavioral details: 'This is a pure read despite being an HTTP POST', the response maps each calendar id to busy ranges, 'Only busy blocks come back – never event titles or details', transparent events are excluded, and inaccessible calendars appear under errors. These disclosures go well beyond what annotations and schema provide.

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 structured and front-loaded: it starts with the primary output, then explains usage, response behavior, and the read-only nature. Every sentence contributes value with no fluff or repetition. Although it is relatively long, each part is necessary for correct use.

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 tool's complexity and the absence of an output schema, the description fully covers input requirements, output format, error handling, and the distinction from other operations. An agent has everything needed to call it correctly and interpret results.

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 schema covers all parameters with descriptions, so the baseline is 3. The description adds extra meaning for calendar_ids: 'Input calendar ids (or attendee email addresses, which double as their primary-calendar ids – subject to their sharing settings)', which is not in the schema. This additional semantic context justifies a 4.

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 verb and resource: 'Returns the busy intervals of up to 50 calendars in one time window'. It differentiates itself from sibling tools like create_event by explicitly framing itself as 'the way to find a common free slot before create_event', making its purpose unmistakable.

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 ('the way to find a common free slot before create_event') and input guidance (calendar ids or attendee emails). However, it does not explicitly state alternatives or when not to use it, so it falls short of a 5.

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