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

Beyond the annotations (readOnly, idempotent, non-destructive), it discloses genuinely non-obvious behavior: pure computation with no calendar access, DST-aware results, ranked top-5 slots, per-zone offset/abbreviation, and an optional ICS VEVENT for the top slot. This is meaningful context the structured fields do not carry.

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?

Front-loaded with the required input ('Given 2-5 IANA time zones') and then the output, with no filler sentences. The single sentence is dense and packs many clauses, but every clause carries information.

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 an output schema present and annotations covering safety, the description need not explain return structure, and it still adds DST behavior, ranking and ICS output. The one gap is routing guidance relative to the search_timezones sibling, but overall it is sufficient to call the tool correctly.

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 the schema already documents defaults, ranges and formats for every parameter. The description largely restates those same defaults (09:00-17:00, up to 7 days, up to 5 slots) and adds little syntax or semantic detail beyond them, 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 ('returns up to 5 ranked meeting slots' across IANA time zones) with the exact inputs it consumes (2-5 zones, working window, up to 7 days). It is clearly distinguishable from the sibling search_timezones, which looks up zone ids rather than computing overlap.

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 intended use (cross-time-zone meeting overlap) is implied clearly by the description, and it notes 'no calendars are read' and the BASIC plan equivalence. However, it never explicitly says when to prefer this over search_timezones or any other scheduling tool, and gives no exclusions or prerequisites.

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