update_event

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

Annotations already indicate destructiveHint=true and readOnlyHint=false. The description adds rich behavioral detail: only passed fields change, others keep current values; recurring event behavior with span; read-only calendar rejection; and alarm replacement semantics. It also explains how to obtain eventIdentifier. This goes well beyond the annotations and discloses important side effects and constraints.

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 description is four concise sentences, each carrying meaningful information without redundancy. It front-loads the primary action and partial-update behavior, then addresses recurring events, read-only rejection, and alarms in a logical order. There is no filler or repetition.

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 11 parameters, the description covers the most critical aspects: partial update, recurring event logic, read-only rejection, and alarm replacement. It does not mention return values (no output schema), error handling, or edge cases like date format validation, but these are arguably less essential. Given the complexity, it is sufficiently complete for an agent to call it correctly in common scenarios.

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 all parameters have individual descriptions. The tool description adds global semantics: partial update behavior, recurring event handling (span and occurrenceDate interplay), and alarm replacement. It also gives provenance for eventIdentifier. This adds value beyond the schema's per-field descriptions, so a score above the baseline 3 is warranted.

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 clear verb+resource: 'Changes an existing event.' It also clarifies the partial-update semantics, which is the core behavior. It implicitly distinguishes from siblings like create_event and delete_event, and the phrase 'Get eventIdentifier from list_events' ties it to the correct data source. This is a precise, non-tautological purpose.

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 gives specific guidance: get the identifier from list_events, and for recurring events pass occurrenceDate and span with explicit meaning of each span value. It also notes that read-only calendars are rejected, implying you should ensure the calendar is writable. It does not explicitly name alternatives (e.g., 'use create_event for new events'), but the context of updating an existing event is clear. This is strong but not exhaustive.

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