Update Event

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

The description discloses partial-update behavior and specifies that in cloud mode, recurrence, invitees, and alarms are preserved via CalDAV property-merge. It also flags the feature as experimental with live round-trip unverified. This goes well beyond the annotations, which only indicate non-read-only, idempotent, and non-destructive characteristics.

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, with the core action front-loaded in the first sentence. It then provides the single most important behavioral nuance and a risk caveat, with no 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?

Given the tool's complexity as an update operation with mode-specific behavior, the description covers purpose, update semantics, cloud-mode preservation, and experimental status. Without an output schema, this is sufficient for correct invocation. The only omission is explicit local mode behavior, but that is handled by the eventUrl parameter description.

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 schema documents all six parameters with descriptions, covering 100% of parameter semantics. The description adds the crucial partial-update rule: only fields passed are changed, which is not evident from the schema alone. This clarifies how omitted optional parameters behave.

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 clearly states the action: 'Updates an existing calendar event.' This distinguishes it from create-event and delete-event by focusing on modifying an existing entity. The additional note about partial updates further clarifies the tool's scope.

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 the appropriate use case: modifying fields of an existing calendar event. It does not explicitly name alternatives, but the context is evident from the sibling tool list, and the partial-update statement guides when to use it. The cloud-mode note provides mode-specific context, but no explicit when-not-to-use.

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