update_event

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

With no annotations, the description carries the full burden and does deliver genuinely non-obvious behavior: partial updates, and that moving `start` alone preserves duration rather than shifting the whole event. It omits permissions/error behavior and, more importantly, does not warn that `scope: series` mutates every occurrence of a recurring event — a destructive consequence the agent should know about.

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?

Three short sentences, front-loaded with the core action, then the two constraints that matter most. No filler and nothing repeated from the schema.

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 11-parameter mutation tool with no annotations and no output schema, the description covers the two areas most likely to cause wrong calls: duration drift and recurrence scoping. Gaps remain around `id` validity, failure modes, and the blast radius of series updates, preventing a 5.

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 64%, and the description reinforces the two trickiest parameters: `start` (duration preserved when moved alone) and `scope` (required for recurring events). However, the only required parameter `id` is undocumented in both schema and description, and it doesn't clarify edge cases like whether changing `rrule` on a recurring event requires a particular scope.

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?

"Change an event" is a specific verb plus resource, and the partial-update framing distinguishes it in practice from create_event and delete_event. It never names a sibling explicitly, so differentiation is implied rather than stated.

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?

Clear operating context: patch semantics ("only the fields you pass change") tells the agent to use this rather than delete-and-recreate, and "For recurring events pass `scope`" is a concrete conditional instruction. It stops short of stating exclusions or naming alternatives such as create_event/delete_event for the cases this tool shouldn't handle.

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