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

Annotations already establish readOnlyHint=true, destructiveHint=false and openWorldHint=false, so the safety profile is covered by structured data. The description adds genuine extra context: a default 30-minute minimum window and a two-member precondition. It does not say what happens when the precondition fails, nor what a returned window contains (no output schema exists), which limits it to a 3.

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 short sentences, with the core behavior first and the constraint second; every clause carries information and nothing is padded.

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 simple read-only query tool this is close to adequate, but with no output schema the description should say what a "free window" looks like (start/end times, per-member vs aggregate). The relationship between the hardcoded 30-minute mention and the min_minutes parameter is also left ambiguous.

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%, and each parameter (date_from, date_to, member_ids, min_minutes) is documented in the schema itself, so baseline is 3. The description's "(>= 30 min)" hints at the default for min_minutes, which is a small addition, but it never clarifies how that stated threshold interacts with a caller-supplied min_minutes value.

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?

"Find shared free windows ... across household members in a date range" gives a specific verb and resource plus the key qualifier (shared, across members), so an agent knows this returns common availability rather than one person's calendar. It stops short of explicitly distinguishing itself from likely neighbors like get_busy_blocks or get_schedule_conflicts, so it is clear but not sibling-differentiating.

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?

"Needs at least 2 members" is a useful precondition that implies the tool is for multi-member coordination, and the shared-window framing implies when it applies. However, there is no explicit guidance on when to prefer this over get_busy_blocks or get_schedule_conflicts, and no statement of what to do if fewer than 2 members exist.

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