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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint=false, so the safety profile is covered. The description adds genuinely new behavioral context: a per-call cost of $0.001 via x402 and the 7,000+ city coverage, both of which affect whether an agent should batch calls. It stops short of describing error behavior for unknown or ambiguous cities.

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?

A single dense sentence with the core capability front-loaded, followed by examples, scale, and cost. No filler or redundancy.

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?

An output schema exists, so return values need not be explained, and the cost and coverage details round out the picture. The main gap is the absence of guidance on ambiguous-name resolution and on how 'at' interacts with the returned local time.

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 50%, and the description clarifies that cities are passed by name and that country disambiguates common names like Springfield, which adds real meaning beyond the schema. It says nothing about the 'at' parameter or the city-vs-cities exclusivity, leaving half the parameters to the schema alone.

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 ('Find the IANA time zone and current local time') plus scope ('up to 10 cities by name') and coverage ('7,000+ cities'). It does not explicitly distinguish itself from siblings like timezone_convert or public_holidays, so an agent must infer that this is a name-based lookup rather than a conversion.

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 parenthetical '"Springfield" + country' implies when the country parameter is needed for ambiguous names, and 'up to 10 cities' signals batching. However, there is no explicit when-to-use versus timezone_convert or public_holidays, and no statement of what happens when a name is ambiguous and country is omitted.

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