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

Annotations already declare readOnly, idempotent, and non-destructive, so the safety profile is covered. The description adds genuinely new behavioral context: results are in the organization's timezone, all-day items are returned as dates rather than times, and mutability is restricted to type EVENT. It does not describe pagination or ordering, which is a minor residual gap.

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 sentences, front-loaded with the core purpose, then timezone semantics, then the get_date prerequisite, then the mutation caveat. No sentence is redundant and nothing important is buried.

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?

With no output schema, the description carries the burden of describing results, and it does so by naming the five item categories and their time representation. Combined with annotation-covered safety and full schema coverage, an agent has enough to call this correctly; only ordering/pagination behavior is unstated.

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 coverage is 100%, so the baseline is 3, but the description earns an increment by explaining what each item type actually means in results (task due dates vs invoice due dates vs project deadlines) and by emphasizing the organization-timezone interpretation of from/to. It does not restate the inclusive-end semantics, which the schema already handles.

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 uses a specific verb and resource ('List what's on the calendar between two dates') and then enumerates exactly what is aggregated: events, task due dates, invoice due dates, project deadlines, and expense dates. That enumeration distinguishes it from single-domain siblings like list_tasks or list_invoices without the agent opening any 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?

It gives a concrete sequencing rule — 'Use get_date first for relative ranges like this week' — which is exactly the prerequisite an agent would otherwise get wrong. It also closes the loop on follow-ups by noting only EVENT items are mutable via the calendar event tools. It stops short of explicitly contrasting with the per-domain list tools, so it is clear but not exhaustive.

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