update_event

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

Annotations declare readOnlyHint=false, idempotentHint=true, destructiveHint=false. The description goes beyond these by disclosing the ETag-based concurrency conflict behavior and the partial-update semantics. It also explains clearing fields with empty strings, adding significant behavioral context not available from annotations or schema.

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 well-structured: opening with the core action and partial-update note, followed by concurrency detail, then a clear Args list, and a Returns line. Every sentence adds value; no filler. The most important information is front-loaded, and the parameter documentation is efficient.

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 9 parameters and an output schema, the description covers all necessary aspects: what it does, how partial updates work, concurrency behavior, parameter semantics, and the return value. The output schema exists but the description summarizes the return ('Confirmation message with the updated event UID'). It does not mention error cases beyond conflict, but that is acceptable given the ETag note.

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 0%, so the description carries full responsibility for parameters. It provides an Args section that explains all 9 parameters, including formats (ISO 8601 for start/end), allowed values (status enum), and clearing semantics. This far exceeds the schema's bare names and types, making it easy for an agent to construct correct arguments.

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's purpose: 'Update an existing calendar event.' This uses a specific verb and resource, and the word 'existing' distinguishes it from create_event. The sibling list includes create_event, get_event, delete_event, so the update intent 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 by saying 'existing calendar event' and points to get_events for finding UIDs. It also explains partial update behavior ('Only provided fields are changed') which is key to using it correctly. However, it does not explicitly contrast with create_event or mention scenarios where update is not appropriate, leaving some inference to the agent.

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