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

Annotations already declare readOnlyHint=false, destructiveHint=false and openWorldHint=true. The description adds real value beyond those: partial-update semantics ('Only the fields you pass change'), the visibility consequence ('Edits to a published event are visible to members and attendees'), and the confirmation/API-key requirements. Only the return/response behavior is left unstated.

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 first sentence is front-loaded and clear, but the second sentence ('Changes fields of an upcoming event') redundantly restates it, and the trailing confirmation/API-key boilerplate dilutes focus. Sized acceptably but not tight.

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 two-parameter update tool with 100% schema coverage and no output schema, the description covers the mutation's scope, side effects, and confirmation workflow well. Only the result/response shape is unaddressed, which is minor given no output schema exists.

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% and the schema already enumerates the accepted field values; the description restates a similar but slightly less precise set ('time' vs start_time/duration_minutes). It adds the partial-update rule but no per-parameter syntax, so baseline 3 is appropriate.

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?

States a specific verb (change) and resource (upcoming event) plus the exact editable fields (title, time, description, venue, attendee limit), which lets an agent distinguish it from read/organizer siblings. It does not name a sibling alternative to route against, but the scope 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?

The description implies usage constraints ('an upcoming event', confirmation default, 'confirm with the user before each call') but never states when to choose this over create_event, copy_event, or cancel_event. Usage context is implied rather than explicit.

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