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

Discloses the key limitation that it returns only times and never event titles, which is useful. However, with no annotations, it doesn't mention authentication, rate limits, or whether it returns only busy blocks (it implies busy blocks but doesn't clarify). It provides some behavioral context but not comprehensive.

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?

Two sentences, front-loaded with the core purpose, no wasted words. The structure is efficient and immediately conveys the tool's function and a key constraint.

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?

For a tool with 4 parameters, no output schema, and no annotations, the description is too sparse. It omits parameter semantics, usage guidance, and deeper behavioral details like time format or calendar selection. An agent would be under-informed to call it correctly.

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 only 25% (only mailbox has a description). The tool description adds nothing about timeMax, timeMin, or calendarId parameters. Since coverage is low, the description should compensate, but it doesn't, leaving three parameters undefined.

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?

States the specific function: returning busy blocks on a calendar so a free slot can be proposed. It explicitly differentiates from event listing by noting 'Returns times only, never event titles,' which distinguishes it from list/search calendar event tools. The platform is clear from the tool name, though the description is generic.

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?

No guidance on when to use this tool versus alternatives like find_google_calendar_busy_times or list_outlook_calendar_events. It doesn't mention prerequisites, exclusions, or conditions that would select this tool over siblings.

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