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

No annotations are provided, so the description must disclose behavioral traits. It only states 'darken a color by a percentage' without explaining whether it modifies the input, how it handles invalid hex values, or what the output format is. The behavior of the 'amount' parameter is not clarified (e.g., relative to current lightness or absolute).

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?

The description is a single sentence with no unnecessary words. It is front-loaded and efficient. However, it could benefit from a bit more detail about the parameter semantics, which would improve clarity without significantly increasing length.

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?

Given the tool's simplicity and full schema coverage, the description is functionally adequate. However, it lacks usage guidance and behavioral context, which would improve completeness for an AI agent selecting among many color manipulation tools. The presence of an output schema compensates for not explaining return values.

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 have descriptions in the input schema (100% coverage). The description does not add any additional meaning beyond the schema. For example, it does not explain how 'amount' is applied (e.g., subtract from lightness or reduce by percentage). Baseline 3 is appropriate.

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 clearly states the verb 'darken' and the resource 'color', specifying the method 'by a percentage'. It distinguishes this tool from sibling tools like lighten_color, saturate_color, and desaturate_color by the specific operation.

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 provides no guidance on when to use this tool versus alternatives. It does not mention when darkening is preferred over lightening, desaturating, or other color operations. Sibling tools like lighten_color and saturate_color exist but no differentiation is given.

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