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

Annotations already cover the safety profile (readOnlyHint=true), and the description adds genuinely useful behavioral detail beyond it: recurring series are expanded, Google OOO events count as busy (opaque), and workingLocation events do not. It does not describe the return shape, but the busy-detection semantics are a substantial addition.

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?

Four sentences, purpose front-loaded, then progressively finer behavioral detail about busy detection. Every sentence earns its place and nothing is padded.

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 query tool with no output schema, the description conveys what is returned (free time slots) but not their structure or granularity (e.g., whether adjacent slots are merged, per-calendar vs aggregated). It is nearly complete but leaves a small gap on return semantics.

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 75%, so the nested window object, calendars pairs, busyTimezone, and minDurationMinutes are largely documented in the schema itself. The description adds no additional parameter meaning (no format or default elaboration beyond structured fields), so the baseline 3 applies.

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 a specific verb ('Find') and resource ('free (unbooked) time slots'), plus the scope ('within a window across one or more calendars'). This clearly differentiates it from siblings like list_events or get_event, which return events rather than computed free slots.

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?

Usage is implied by the window/calendars framing but there are no explicit when-to-use statements, no exclusions, and no named alternatives (e.g., list_events when the agent wants raw events). The agent must infer the context.

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