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

Annotations already declare destructiveHint=true, and the description adds valuable context by emphasizing this writes to the REAL connected calendar and affects the user's actual data. It also discloses the upsert-by-event_id behavior, which is meaningful beyond the annotation alone.

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 compact: two clear sentences plus the endpoint. It front-loads the core action and side-effect warning without redundant phrasing or unnecessary detail.

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?

Given the complete schema coverage and the destructiveHint annotation, the description provides sufficient context for invoking the tool. It lacks explicit guidance on update behavior for omitted optional fields and does not describe the response, but these are minor for basic invocation.

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 input schema fully documents all parameters. The tool description adds little parameter meaning beyond noting the upsert keyed by event_id and the endpoint, but that doesn't elevate above the baseline.

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 clearly states the tool creates or updates an event via upsert by event_id, identifying the exact resource and action. It also names the API endpoint and distinguishes itself from siblings like cronofy_delete_event and cronofy_read_events.

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 makes the use case clear: create or update a real connected calendar event using event_id for upsert semantics. It does not explicitly contrast with sibling tools, but the operation is self-evident and the 'writes to the user's actual calendar' warning sets appropriate expectations.

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