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

With no annotations, the description carries the burden of explaining behavior. It usefully discloses that missing inputs fall back to documented defaults and lists what the calculation covers, but it omits details such as how extended-day input changes results or what the returned output structure looks like.

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 brief, front-loads the outputs, and separates the fallback rule into a second sentence. The typo 'calculator calculator' is minor and slightly distracts, but the structure remains efficient.

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 is moderately complex with five optional parameters and no output schema. The description compensates reasonably by listing the four result categories and mentioning default fallback behavior, though it does not specify exact return formatting or units.

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 documents every parameter. The description adds only the general note that missing inputs fall back to defaults, which is helpful but does not deepen understanding of individual parameters.

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 clearly identifies the tool as running an HGV drivers' hours calculator and lists four concrete outputs it produces. It is distinct from sibling tools like calculator_describe, though the repeated word 'calculator' and lack of explicit sibling differentiation prevent a perfect score.

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 gives no guidance on when to use this tool versus calculator_describe or the enquiry tools. It states a fallback behavior for missing inputs but never explains the intended scenario or selection criteria.

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