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

Annotations already declare readOnlyHint=false, destructiveHint=false, and idempotentHint=false, so the safety profile is covered. The description adds genuinely new behavioral context the annotations do not carry: admin permission is required and the plan may cap the number of sub-calendars. The non-idempotency sentence restates the annotation, slightly diluting the added value.

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?

Four short sentences, front-loaded with the WRITE flag and the action, then prerequisites, then the non-idempotency warning, then the endpoint. Nothing is bloated, though the non-idempotency sentence largely duplicates the idempotentHint annotation.

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 low-complexity create tool with full schema coverage and annotations covering safety, the description supplies permissions, plan limits, idempotency behavior, and the endpoint. The only real gap is the return value (e.g. the new sub-calendar's id), which matters since no output schema exists.

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% – all four parameters (name, color, active, overlap) already have inline descriptions, type constraints, and defaults. The description adds no parameter-level meaning such as name uniqueness or color semantics, so the baseline 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 opens with a specific verb+resource pair ('WRITE: create a sub-calendar') and names the HTTP operation, so its identity is unambiguous. 'Create' versus the sibling teamup_update_subcalendar is self-evidently differentiated, and no schema inspection is needed to tell them apart.

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?

It states preconditions (a calendar key with admin permission, possible plan limits on count), which is useful context for when the call will succeed. However, it never names an alternative or an exclusion, e.g. when to call update_subcalendar or list_subcalendars instead; usage is only implied by the verb.

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