create_event

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

The description discloses a non-obvious behavior: event creation is local and external calendar sync only happens if the Marvin client app is running. This adds value beyond the annotations, which are all false and provide no safety profile. The 'EXPERIMENTAL' label further signals risk.

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 two sentences. The first sentence delivers the purpose immediately, and the second adds a critical caveat. There is no wasted wording 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?

Given the fully documented schema and the presence of an output schema, the description covers the essential creation context and the important client-sync dependency. It lacks only usage-alternative guidance, which is a usage-guidelines gap rather than a completeness 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% with descriptions for all four parameters, including an ISO 8601 format example for start_iso and an exclusiveMinimum constraint for length_minutes. The description itself adds no extra parameter semantics, so the baseline score of 3 applies.

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 and resource: 'Create a calendar event.' This distinguishes it from sibling tools like create_task, create_time_block, and create_category_or_project. The 'EXPERIMENTAL' prefix does not obscure the core 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 no guidance on when to use this tool versus alternatives such as create_time_block or create_task. The sync caveat describes a behavioral constraint but does not explain when this tool is appropriate or when a sibling should be chosen instead.

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