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

The annotations already establish that this is a read-only, idempotent, non-destructive operation, so the safety profile is covered. The description adds the useful detail that it reads from one connected calendar and where the required calendar identifiers come from, but it says nothing about date-range defaults, timezone behavior, or return shape.

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 wasted wording. The scope is front-loaded, followed by the key prerequisite for obtaining the required identifiers.

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 annotations covering safety and no output schema, the definition is adequate for a simple read operation only at a minimum level. It is missing important operational context about the date range and timezone parameters, which an agent would need to call it correctly and interpret results.

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% across six parameters, so the description must carry parameter meaning. It only explains the provenance of credentialId and externalId; it leaves dateFrom, dateTo, timeZone, and loggedInUsersTz entirely undocumented, despite date range being central to a busy-intervals query.

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: read busy intervals from one connected calendar. It is clear enough to act on, but it does not differentiate this tool from similar siblings such as get_calendar_freebusy, get_connection_freebusy, or get_user_availability.

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 only usage context is that credentialId and externalId come from list_calendars, which is a prerequisite rather than guidance on when to choose this tool over alternatives. There is no explicit when-to-use or when-not-to-use guidance relative to the many free/busy and availability siblings.

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