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

With readOnlyHint/openWorldHint already covering the safety profile, the description adds substantial non-obvious behavior: gaps derive only from scheduled jobs and logged absences, working hours and travel time are excluded, and results are candidates rather than confirmed free time. It also points at a returned `note` field the agent should read, which annotations alone would not reveal.

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 sentences, both load-bearing, front-loaded with the core action and immediately followed by the most important caveat. No filler or restatement of the name.

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 a four-parameter read tool with no output schema, the description covers the data-source limitation, the confirm-before-promising rule, and flags a return field. The only gap is the shape of the returned gaps themselves (e.g., list of intervals), which is a minor omission since the core semantics are conveyed.

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 from/to/resource_id/slot_minutes are already documented in the schema. The description restates slot_minutes' filtering role ('ignoring gaps shorter than slot_minutes') but adds no format or edge-case detail beyond the schema, so the baseline 3 applies.

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: finding gaps in one engineer's day within a time window, with the slot_minutes threshold made explicit. The scope (one engineer, scheduled jobs and logged absences only) is distinctive enough that an agent can tell it apart from siblings like get_schedule or find_resource without opening either 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 downstream usage guidance ('treat a gap as a candidate to confirm with the user, not a promise') but never states when to choose this tool over get_schedule or find_resource, or any prerequisite for calling it. Usage is implied by the output caveat rather than explicitly framed as when-to-use.

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