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

With no annotations provided, the description carries the full burden of behavioral disclosure. It reveals that the conversion preserves the same instant and is DST-aware, which is critical context beyond the schema. However, it does not mention potential edge cases like ambiguous/nonexistent times, error handling for invalid timezone IDs, or the exact output structure, leaving a small gap for a timezone conversion tool.

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 well-structured and front-loaded with the core action in the opening sentence. The 'Use when' and 'Do not use when' sections are concise, scannable, and each bullet adds direct value. No superfluous sentences; the length is justified by the clarity it provides for tool selection.

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?

The tool has moderate complexity with DST awareness and three required parameters. The description covers purpose, usage guidelines, and key behavioral traits, and the schema covers parameter semantics. There is no output schema, but the description does not explicitly state the return format (e.g., does it return the converted ISO string with an offset?), which would enhance completeness. Overall, it is nearly complete but leaves a minor gap.

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 thoroughly documents each parameter (datetime, from_timezone, to_timezone). The description adds example usage and clarifies the role of from_timezone for naive datetimes, but this largely mirrors the schema descriptions. It does not introduce new parameter-level semantics beyond what the schema provides, so the baseline of 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 states a specific verb ('Convert'), a clear resource ('ISO-8601 datetime'), and the exact transformation ('from one IANA timezone to another while preserving the same instant'). It also highlights DST-aware behavior and gives a concrete example (Toronto to Tokyo), which clearly distinguishes it from sibling tools like timestamp_convert and unit_convert.

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 description provides explicit 'Use when' examples (e.g., 'What time is 3pm Toronto in Tokyo?') and explicit 'Do not use when' exclusions with named alternatives (timestamp_convert, unit_convert). This gives an agent clear decision criteria for selecting this tool over siblings.

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