Calendar Update Event

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

Annotations already indicate destructiveHint=true and readOnlyHint=false, so the description doesn't need to restate that this is a mutating operation. The description adds valuable behavioral context: partial updates ('Only provided fields change') and the whole-series behavior for recurring events. It also implicitly warns that updates to recurring series affect the entire series, which is important for an agent to know. It doesn't mention side effects like invitation sending, but the schema covers that for attendees.

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 sentences, zero filler. The first sentence states the action and the partial-update behavior; the second sentence adds the critical recurring-series caveat. Every word earns 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 a mutation tool with 10 parameters, the description is concise but the schema carries the parameter details. The description covers the two most important behavioral nuances: partial updates and whole-series recurrence. It doesn't mention that attendees replacement sends invitations, but that is in the schema's parameter description. Given the output schema exists and annotations cover the destructive nature, this is nearly complete.

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 schema already documents all 10 parameters thoroughly. The description adds the key semantic that only provided fields change, which is critical for understanding the null-default pattern. However, it doesn't add much beyond that because the schema already explains each parameter's meaning and special values (e.g., empty string clears). 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?

The description states a specific verb ('Update') and resource ('fields of an existing event'), and immediately distinguishes itself from create/delete siblings by clarifying that only provided fields change and that recurring series are updated as a whole. This is clear and 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 when to use this tool: to modify an existing event, as opposed to creating or deleting. It does not explicitly name alternatives or exclusions, but the context of sibling tools and the phrase 'existing event' provide clear usage context. A slightly stronger statement about when not to use it (e.g., for creating events) would earn a 5.

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