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

Annotations already state non-read-only, non-idempotent, and non-destructive behavior. The description adds value by specifying that only explicit fields are updated (behavioral detail not in annotations) and by warning against retrying after ambiguous failures, which indicates partial-application risk. These traits are beyond what annotations 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 two sentences: the first states the primary purpose, the second gives two critical operational warnings. It is front-loaded and concise with no filler or redundant information.

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 mutation tool with 17 parameters, no output schema, and low schema coverage, the description is too sparse. It does not explain return values, how unspecified fields are treated, provider-specific behaviors (only the notify parameter hints at Google-specificity), or account selection steps. The two warnings are helpful but insufficient for complex edge cases.

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 only 35%, so the description should compensate. However, the only parameter-related guidance (event_id paired with calendar_id) is already present in the schema's event_id description. No additional meaning is provided for the other 15 parameters, such as start, end, attendees, or recurrence.

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 'Update explicit fields on a resolved event' with a specific verb and resource, and the 'resolved' qualifier distinguishes it from creation and other calendar operations. This clearly differentiates it from siblings like calendar_create_event and calendar_update_calendar. The phrase 'explicit fields' also signals a partial update rather than a full overwrite.

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 implies usage after resolving an event (by mentioning 'resolved event') but does not explicitly contrast with alternatives like calendar_create_event or calendar_cancel_event. It gives operational guidance (pairing event_id with calendar_id, avoiding blind retries) but lacks an explicit when-to-use or when-not-to-use statement, leaving some inference to the agent.

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