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

Annotations already declare a non-read-only, non-idempotent mutation. The description adds the provider scope but does not disclose further behavior such as duplicate handling, immediate visibility, or external side effects. There is no contradiction with annotations, but the description contributes little beyond the obvious creation action.

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 with no wasted words. The core action is front-loaded in the first sentence, and the usage guardrail is in the second. Perfectly sized for the tool's simplicity.

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 straightforward creation tool with annotations covering the write nature, the description plus the detailed account_id parameter guidance are sufficient to invoke the tool correctly. The only notable omission is any indication of the return value, but no output schema exists, so this is a minor gap.

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 description itself does not expand on individual parameters, but the schema already covers 3 of 5 parameters (timezone, account_id, background_color) with descriptions. The remaining parameters, name and description, are self-explanatory. The account_id parameter description is especially rich, providing operational guidance beyond basic semantics.

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 ('Create') and resource ('calendar') with the account scope ('selected Google or Microsoft account'). It explicitly differentiates from the sibling calendar_create_event by adding 'not merely an event,' so an agent can immediately tell which creation tool is appropriate.

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?

Provides a clear when-to-use condition: 'Use only when the user explicitly asks for a new calendar, not merely an event.' Additionally, the account_id parameter description gives detailed guidance on when to omit versus when to list accounts and ask, preventing incorrect multi-account selection.

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