update_calendar_event

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

Annotations already declare mutability, non-destructive, non-idempotent and closed-world, so the safety profile is carried. The description adds the return shape and hints that only supplied fields change, but stays silent on what happens with an invalid eventId, whether changing startsAt shifts endsAt, and it never mentions the allDay parameter's effect. Adequate, not rich.

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?

Front-loaded purpose, then usage, then params, then return — a clean and scannable shape. The parameter list is largely redundant with a 100%-documented schema and even drops one property, so a sentence or two does not earn its place.

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 an 8-param mutation with no output schema, the description covers the required ID, its provenance, the updateable fields, the return value, and when to reach for it. The unmentioned allDay flag and the lack of any partial-update or error semantics are the remaining gaps.

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. The description mostly restates schema text verbatim, with one genuine addition: it tells the agent the eventId comes from get_calendar_events. It also omits the allDay parameter entirely, so it is neither complete nor value-adding beyond the schema.

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 first sentence gives a specific verb and resource ("Update an existing calendar event") and the CRUD sibling set (create_calendar_event, delete_calendar_event) makes the scope unambiguous. Three concrete example utterances pin down what "update" means in practice.

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?

A dedicated "Use this when" block with three realistic trigger phrases gives clear positive routing. It lacks any exclusion or alternative (e.g. when to use create_calendar_event instead, or what to do for a recurring event), so it stops short of full when/when-not guidance.

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