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

The description adds useful semantics not present in the annotations: events marked free are ignored, whole-day events block the entire day, and a 31-day limit is indicated. These rules materially change the result and would be easy to miss. It does not mention side effects or auth needs, but the annotations do not establish a read-only profile, so the description carries more of the transparency burden than in a tool with readOnlyHint=true.

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 compact and front-loaded: the core behavior appears first, followed by edge-case rules and the sibling pointer. The cryptic 'Free: 31 days' costs a little clarity; otherwise this would be excellent for size and structure.

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?

There is no output schema, and the description only characterizes the result as 'merged busy blocks and free gaps' without specifying response structure or how zone/calendars influence the output. It does cover core event-filtering rules and the conflicts alternative, making it usable, but an agent would still have to assume return format details.

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%, so every parameter including from, to, zone, work_start, work_end, and calendars is already explained by the schema. The description only adds 'working hours' and the cryptic 'Free: 31 days,' neither of which materially deepens parameter understanding. Baseline 3 is appropriate.

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 clearly identifies the tool's deliverable: 'Merged busy blocks and the free gaps inside your working hours over a day range.' It also distinguishes from the 'conflicts' sibling by pointing out the overlap-pair use case. It lacks an explicit action verb such as 'Get' or 'List,' so it falls just short of a 5.

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?

'Use conflicts for overlapping pairs' is an explicit alternative and a clear when-not signal for overlap analysis. The rest of the description implies this tool is for aggregate availability over a day range, which is useful context. It does not spell out when to choose events_list/events_search instead, so the guidance is good but not complete.

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