lookup_timezone

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

With no annotations, the description carries the full behavioral burden. It discloses the full return contract, including valid, is_dst, and cost_usd, and notes it uses Python's stdlib zoneinfo, implying no network/auth dependency. It does not explain invalid-timezone behavior explicitly, but the valid key signals it.

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 organized into Intro, Args, and Returns sections, which is easy to parse. There is mild redundancy between the opening sentence and the Returns block, but no wasteful content.

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 single-parameter lookup with no output schema and no annotations, this description is complete: it documents the parameter format with examples, names the implementation, and enumerates the exact return keys. Nothing needed for correct invocation is missing.

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 coverage is 0% and the schema only labels the parameter 'Timezone'. The description compensates fully with 'timezone: IANA timezone name' and concrete examples like America/New_York and Europe/London, giving the agent exactly what it needs to format the argument.

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: 'Look up timezone information by IANA timezone name.' The returned fields (UTC offset, DST status, abbreviation, local/UTC time) make it clearly distinct from the sibling convert_timezone, which would convert between zones rather than describe one.

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 clear context for when to use this tool: when an agent needs current timezone metadata for an IANA name. It does not explicitly name alternatives or exclusions, but the return-field listing makes the intended use obvious.

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