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

Annotations already mark it read-only and idempotent; the description adds the exact conversion factor and that both values are returned, which is meaningful behavioral detail beyond schema and annotations. No contradiction is present.

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?

Three short sentences, with the operation and factor first and the ancillary source URL last. No redundant phrasing or unnecessary detail.

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 complete input schema, an output schema, and annotations covering read-only and idempotence, the description covers the remaining needed context: what to pass, the factor, and that both values come back. Nothing important is missing for a simple converter.

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?

Both parameters are fully described in the schema, including the enum for the unit, so the description's restatement of 'amount and unit' adds little. It reinforces the flow but does not meaningfully enrich parameter semantics beyond the schema.

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 conversion operation (kcal ↔ kJ) with the exact factor, immediately differentiating it from the many other converter siblings. The resource and direction are 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?

The description tells the agent to supply an amount and a unit, and frames the tool as the food-energy converter, which makes the intended context clear. It doesn't explicitly discuss alternatives or exclusion cases, but none are material for such a unique unit pairing.

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