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

Annotations only declare destructiveHint=true; the description adds meaningful context beyond that — the partial-update semantics, an explicit user-confirmation requirement before mutation, and the multi-account `account` prerequisite. It does not describe rate limits or notification side effects of the mutation itself, but it substantially enriches the safety picture.

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 short sentences, front-loaded with the patch semantics, then format rules, then the confirmation warning. Every sentence carries operational information; minor redundancy between the description and the schema's start description is the only inefficiency.

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 14-parameter destructive mutation with no output schema, the description covers the critical behaviors: partial update, format rules, confirmation, and account selection. Attendee/recurrence replacement semantics live in the schema, so the agent has what it needs without the description duplicating them.

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 100%, so the baseline is 3, but the description adds cross-parameter meaning: the start/end format rules, the all_day interaction for changing an all-day event's date(s), and the account requirement. This goes beyond restating individual schema fields.

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 (Patch) and resource (Google Calendar event) and immediately clarifies the patch semantics: 'only the fields you pass are changed, everything else is left as-is.' This clearly separates it from create_calendar_event and delete_event.

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?

Gives explicit operating conditions: confirm with the user before calling, pass `account` when multiple calendar accounts are connected, and reference create_calendar_event for format rules. It does not contrast against sibling mutation tools like respond_to_event, but the context provided is concrete and actionable.

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