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

With no annotations provided, the description carries the behavioral disclosure burden. It does disclose that this is a write operation and that there is no credit cost, which is useful safety/billing context. It does not mention partial-update semantics, whether unspecified fields are preserved, or any permission requirements, but the core mutation behavior is clear.

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 short sentences with no filler. The primary action is front-loaded, and the additional behavioral notes ('Write operation, no credit cost') are both relevant and efficiently stated.

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 simple update tool, this is adequate but not complete. It does not explain whether omitted optional fields are left unchanged or cleared, nor does it describe what the tool returns in the absence of an output schema. An agent can likely proceed, but some behavior would need to be inferred.

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% and there are six parameters, yet the description provides no detail about id, notes, title, all_day, starts_at, or ends_at. The schema's names and types carry all parameter meaning, and the description does not compensate for the lack of datetime formats, constraints, or update semantics.

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: 'Edit an existing custom calendar event.' It clearly differentiates from sibling tools like crm_create_calendar_event and crm_delete_calendar_event by emphasizing 'existing,' so an agent can identify the intended operation without opening the schema.

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 phrase 'Edit an existing' provides clear context that this tool is for modifying already-created events, not for creating new ones. However, it does not explicitly name alternatives like crm_create_calendar_event or state when-not-to-use, so it stops short of a fully explicit routing guide.

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