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

With no annotations, the description fully discloses the tool's behavior. It explains the paid nature: 'call without x_payment to receive this call's exact terms ... then call again with x_payment.' It also reveals that the free `pricing` tool lists all prices, which is useful behavioral context. The description warns that a call without payment returns terms, not data, making the workflow transparent.

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 about 90 words and front-loaded with the primary purpose. It efficiently explains the views and the payment model without unnecessary filler. It is a bit dense, but every sentence contributes meaningful information. A slight grouping of the payment details could improve scannability, but it's well-structured.

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 8 parameters, no output schema, and a paid workflow. The description covers the main views, the payment flow, and directs users to the `pricing` tool. It doesn't explicitly state the return format for each view, but enough is implied (e.g., 'offset' returns the offset, 'convert' returns the converted time). For the default 'now' view, it says 'current local time', which is sufficient. Given the complexity, this is fairly complete.

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 100%, so the baseline is 3. The description adds semantic meaning by connecting parameters to views: 'at' for offset/business_hours, 'time' and 'to' for convert, and 'open'/'close' for business hours. It also clarifies the x_payment workflow, which the schema describes but the description reinforces. This exceeds baseline.

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 opens with a clear statement of what the tool does: 'Current local time, UTC offset and DST state for an IANA zone.' It then enumerates the distinct views ('offset', 'convert', 'business_hours'), each with a specific behavior, which distinguishes it from sibling tools like weather or holidays. The verb 'answers', 'moves', and 'says' are specific and action-oriented.

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?

Although no alternative tools are explicitly named, the description makes the usage context clear: use 'offset' for a specific instant, 'convert' to move wall-clock time between zones, and 'business_hours' to check if an instant is within business hours. The default view 'now' is implied. This provides clear context but doesn't explicitly state when not to use the tool or point to alternatives, so it falls just short of a 5.

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