Update Calendar Event

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

Annotations already declare it non-read-only and non-destructive; the description adds value beyond them by disclosing the ownership requirement, the specific failure mode (permission error on course events), and partial-update semantics ('Fields you omit stay the same') — a genuine behavioral trait an agent must know to avoid wiping fields. Return payload and undo/reversibility are not described.

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 action, then the constraint, then the update semantics. No filler or restatement of the title.

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 5-parameter mutation tool with no output schema, the description covers the essential risks: ownership, failure mode, and partial-update behavior; annotations cover safety. It omits what a successful call returns and whether start/end must be supplied together, which is a modest remaining gap.

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 earns above that by generalizing the patch semantics ('Fields you omit stay the same'), which the schema only states for the title parameter. It also enumerates the mutable surface (title, times, description), though it doesn't add format or validation detail 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 description opens with a specific verb and resource ('Change the title, times or description of a calendar event') and names the affected fields, so the agent knows exactly what mutates. It doesn't explicitly name the siblings it sits between (create_personal_event, delete_calendar_event), but the verb 'change/update' against an existing event is unambiguous.

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 states a clear precondition/exclusion: only events you own can be changed, and course events return a permission error. That tells the agent when not to call it. It stops short of naming an alternative path for non-owned events (e.g., reserve/cancel flows), so it is clear context without full routing.

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