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

No annotations are provided, so the description carries the full behavioral burden, yet it discloses nothing beyond the arithmetic. It does not say whether mixed unit systems (e.g., miles with km/h) are handled, what happens at zero speed beyond the schema's constraint, or whether the operation is side-effect-free and deterministic.

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 front-loaded sentence with zero filler, stating the computation and its inputs immediately. It is appropriately compact for a simple two-parameter calculator, though it borders on under-specification rather than true concision.

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?

With a rich input schema and an existing output schema, most structural detail is covered, so return values need not be explained. However, the description omits unit-mixing semantics and the unit the resulting duration is expressed in, which matter for correctly calling a units-aware calculator.

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% and both nested unit/value objects are fully documented with constraints, so the schema does the heavy lifting. The description merely restates the two parameters as 'distance' and 'average speed' without adding format, range, or compatibility meaning beyond what the schema already says.

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 and result (calculate journey duration) plus the exact inputs (distance, average speed), which is enough to distinguish it from the sibling convert_* tools. It stops short of explicitly contrasting itself with any named sibling, but the purpose is unambiguous.

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?

There is no guidance on when to use this versus convert_distance, convert_speed, or calculate_fuel_cost, and no prerequisites or exclusions are given. The agent must infer usage purely from the formula.

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