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. It discloses that the tool produces fuel quantity plus cost figures in both km and mile bases, which is useful, but it never states that this is a pure, side-effect-free computation and gives no permission or rate-limit context. Adequate but not rich.

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 that names the operation, the inputs, and the outputs with zero filler. Nothing is redundant and the core purpose appears first.

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 description covers inputs and the general shape of the result. For a pure calculator with no annotations this is nearly sufficient, though a note that it performs no currency conversion (already only in the schema) would round it out.

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 distance, economy, price, and the display-only currency label in detail. The description restates three of the four inputs but adds no unit syntax or constraint meaning beyond the schema. Baseline 3 applies when the schema does the heavy lifting.

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 ('Calculate') and resources ('fuel required and journey cost') and names the exact inputs (distance, fuel economy, fuel price). This clearly separates it from the convert_* siblings, which transform units rather than compute costs. It stops short of naming a sibling directly, so it lands at 4 rather than 5.

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?

Usage is implied by the input list: an agent can infer this is the tool for turning distance + economy + price into a cost. However, there is no explicit when-to-use guidance and no reference to alternatives such as convert_fuel_economy or calculate_journey_time, so routing is left to inference.

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