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

Annotations already declare readOnly/idempotent/non-destructive/openWorld=false, so the safety profile is covered. The description adds behavior annotations don't: DST is resolved for the specific date, and the tool returns an overlap window in addition to conversions. It does not describe how out-of-range or DST-ambiguous times are handled, which keeps it below 5.

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?

Three sentences, front-loaded with the primary operation and ending with the sibling exclusion. The middle sentence's example list slightly overlaps the first sentence's use-case framing, but nothing is wasted.

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, return values need not be explained, and scope limits (24 zones, 1–12 targets) are stated. Remaining gap is DST edge-case handling for ambiguous/nonexistent local times, which matters for a date-sensitive converter.

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%, including formats and the enum list, so the baseline is 3. The description only points to the schema for zone ids and mentions the 24-zone limit; it adds no format, default, or semantics beyond that.

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 concrete verb and resource ('convert one date and clock time from a source time zone to other time zones') and adds a non-obvious secondary capability (finding the 9 AM–5 PM overlap window). It also names the sibling it is not (time_duration_between), so an agent can distinguish it without opening the 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?

Gives explicit use cases ('schedule across offices', 'pick a meeting time for a distributed team', the 3 PM Eastern in London example) and an explicit exclusion routing duration questions to time_duration_between. When-to-use and when-not-to-use are both present.

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