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

Annotations already declare readOnlyHint=true, idempotentHint=true and destructiveHint=false, so the safety profile is fully covered by structured data. The description adds only that a result is returned; it says nothing about edge cases such as zero/invalid values or the fact that a fuel-economy conversion is non-linear (L/100km is inversely related to mpg).

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?

Short and front-loaded: purpose, use case, inputs, return, cross-reference, in that order. The literal "Returns: {input}" is a cryptic placeholder that reads as a template artifact, costing it a point.

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?

For a three-parameter, pure-function conversion with a full schema, complete enums, an output schema and full annotation coverage, the description supplies everything an agent needs to call it correctly. Nothing material is missing.

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% and both from/to carry enums with descriptions, so the schema already carries the parameter burden. The description's restatement ("Inputs: value, from, to") and unit list add no meaning beyond what is already documented.

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 (convert) and resource (fuel consumption) and enumerates all four supported units, so the operation is unambiguous. It does not, however, distinguish itself from the very close sibling calculate_fuel_economy_conversion, which an agent could easily pick instead.

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?

"Use for car comparison across regions" gives a loose usage context, but there is no when-not guidance and no mention of the near-duplicate siblings (calculate_fuel_consumption, calculate_fuel_economy_conversion). The pointer to list_bundles is a cross-reference, not selection guidance.

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