Mix Two Colours (Pigment Simulation)

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

Annotations indicate readOnlyHint=true, but the description adds that the tool uses 'perceptually modelled subtractive mixing in CIE Lab space', which is not inferable from annotations alone. This provides valuable behavioral context beyond the safety hint.

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 that are directly informative, no fluff. Key information is front-loaded: purpose, model, output, and an illustrative example. Every sentence adds value.

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 output schema exists (handling return values) and the parameters are well-documented, the description covers the tool's purpose, model, example, and behavioral characteristics sufficiently for an agent to understand and invoke it 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?

Input schema already describes all three parameters with 100% coverage, including hex_a, hex_b, and ratio. The description adds an example (Prussian Blue and Yellow Ochre) but does not provide additional semantic nuance beyond the schema, so a baseline score of 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 it simulates subtractive mixing of two colors in CIE Lab space, returning a mixed hex value and the nearest archive match with cultural context. It distinguishes itself from 'RGB screen blending', making its purpose specific and 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 explains what the tool does but does not explicitly state when to use it versus sibling tools like colour_combination or colour_harmonies. An agent lacks guidance on choosing this tool over others in the same domain.

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