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

Beyond the annotations, the description adds useful behavioral detail: partial updates via changed fields only, null clearing for description/location/color, timezone handling for offsetless times, and date-only values for all-day events. It does not elaborate on the destructiveHint=true implications or idempotency, but the annotations already declare those traits.

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 three concise sentences, front-loaded with the core operation and followed by the most important update semantics. Every sentence adds actionable information without redundant repetition of schema or annotations.

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 destructive partial-update tool with 8 parameters and no output schema, the description covers the key invocation semantics well: field-level updates, null clearing, and time/date formatting. It could be more complete by mentioning return behavior or reinforcing destructive effects, but the annotations and schema cover much of the remaining structure.

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 low at 38%, so the description needs to compensate. It adds meaningful semantics for null clearing, timezone interpretation, and all-day date formatting, but it leaves several parameters such as title, allDay, startDate/endDate relationships, and id behavior largely to the schema.

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: 'Change a calendar event.' It also identifies the relevant object type ('type EVENT from list_calendar'), which distinguishes it from create/delete calendar event operations and from updates to other resource types.

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 update use case clear and tells the caller to pass only changed fields, including null to clear certain fields. However, it does not explicitly name alternatives such as create_calendar_event or delete_calendar_event, nor does it state when not to use this tool.

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