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

Annotations already declare readOnly/idempotent/non-destructive, and "Pure calculation: reads and writes nothing" reinforces that the recipe store is untouched, which is useful for an agent reasoning about side effects. It does not cover edge behavior (unknown ingredient, unsupported unit, what happens on a failed density lookup), so it is not exhaustive.

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 sentences, front-loaded with the core purpose, then the exclusion, then the return shape. The worked example earns its place because there is no output schema.

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?

No output schema exists, and the description compensates by spelling out the return object and a concrete example. Combined with annotations covering the safety profile and full schema coverage, an agent has everything needed to call this correctly.

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%, so baseline would be 3, but the description adds real meaning: it explains the density mechanism behind the optional `ingredient` param with a concrete "1 cup flour → grams" example and shows how amount/unit/from map into the result. It does not explain the `to` enum's effect on rounding/precision.

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?

Specific verb+resource ("Convert one cooking amount between units") with an immediately distinguishing scope: single amount vs. whole recipe. It names the sibling it is not (get_recipe units=metric) so an agent can separate the two without opening either schema.

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?

Explicitly routes the agent: use this for one amount, use get_recipe units=metric for a whole recipe. That is a named alternative with the condition that selects it, leaving nothing to inference.

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