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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety bar is low. The description adds real behavioral context beyond that: recurring events appear once per date, results mirror the Calendar tab month view, UTC inputs with display in the calendar's timezone.

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?

Three short sentences, front-loaded with the resource and scope, then return fields, then sibling routing. Only waste is the dangling 'start and end' clause that doesn't map to any parameter.

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?

No output schema exists, so the description carries the return-value burden and does so by naming title, time, place and join eligibility, and by explaining the recurring-event expansion. Month-scoped listing makes pagination less of a concern, though result ordering and empty-month behavior go unmentioned.

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% (group URL name, YYYY-MM month with default), so the baseline is 3. The description adds timezone semantics for times, but it also references 'start and end are UTC' when no such parameters exist in the schema, which muddies rather than clarifies the two real params.

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?

States a specific verb and resource ('Events on a group's calendar in one month') plus the fields returned, and explicitly separates itself from siblings get_event (one event) and create_event (adds one). An agent can pick this apart from neighbors without opening a 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 closing clause routes the agent: get_event for a single event, create_event for creation. It gives clear positive context but never states an explicit exclusion or precondition (e.g., what happens if the group has no calendar or the month has no events).

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