calendar_free_busy

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

With no annotations, the description carries the full burden and does substantial work: it discloses which events are excluded (canceled, declined, all-day by default), how hidden and unsynced calendars are treated, and even surfaces the `unsynced_calendars` output field. It flags that include_unsynced is slow, which is exactly the kind of operational caveat an agent needs. It stops short of stating the return value shape (block granularity, timezone) or that the tool is read-only.

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?

Two compact paragraphs, front-loaded with the return value, then behavioral rules. Each sentence carries a distinct rule (canceled, declined, all-day, hidden, unsynced). Minor deduction for opening with a noun phrase rather than a verb, which reads as a label rather than an instruction.

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 an 11-parameter tool with no output schema and no annotations, the description supplies the essential behavioral model: what counts as busy, what is skipped, and the calendar-inclusion matrix. The gaps are what happens with zero arguments (all params optional, no stated default range) and the format/granularity of the returned busy blocks.

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 would be 3, but the description adds real meaning the schema lacks: the relationship between include_unsynced and the `unsynced_calendars` output, and the fact that sync-off calendars are excluded unless that flag is set. This cross-parameter interplay is not inferable from the individual field descriptions.

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 opening line states precisely what the tool returns: merged busy blocks plus the free gaps between them within a time range. That distinguishes it functionally from calendar_events or calendar_search, but it never names those siblings explicitly, so the differentiation must be inferred from the noun phrase alone.

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?

Usage is implied through the filtering rules (canceled/declined skipped, tentative counted unless disabled), which tells an agent the result is a computed availability view rather than a raw event list. However, there is no explicit 'use this instead of X when…' guidance and no statement about what happens when no range is supplied — all 11 parameters are optional.

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