calendar.events.update

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

With no annotations, the description carries the full burden and does well: it flags SIDE-EFFECTFUL, explains that the merged result is re-validated, and warns that shrinking ends_at below starts_at throws. It also states the return shape `{event}`. It could add permission or conflict details, but the core behavioral risks are disclosed.

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 tight sentences, front-loaded with the safety-critical SIDE-EFFECTFUL marker, then examples, validation behavior, and return shape. Every sentence earns its place with no redundancy.

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?

The schema fully documents all 9 parameters, and the description covers patch semantics, validation, and return value. It is complete enough for a straightforward partial update; missing niceties like auth requirements or conflict behavior are not essential for invoking it correctly.

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 100%, so the baseline is 3. The description adds a cross-parameter constraint not present in the schema: the merged result is re-validated and shrinking ends_at below starts_at throws. This gives meaningful semantics beyond the individual field descriptions.

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 uses a specific verb and resource: 'Patch an existing event', and gives concrete examples (move it, retitle it, re-home it). This clearly distinguishes it from sibling tools like calendar.events.add, calendar.events.delete, and calendar.events.list.

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?

It clearly states this is for modifying an existing event, not creating or deleting one. It doesn't explicitly name alternatives or exclusion conditions, but the context is clear enough that an agent can route to it versus add/delete/list.

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