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

With no annotations provided, the description carries the full burden and does so: it states the tool is 'Read-only and deterministic: it computes a result and stores nothing, so it is safe to call repeatedly with no side effects.' It also discloses per-mode edge behavior (empty-channel domination in paint/cmy, weight sensitivity differences) that an agent could not infer otherwise.

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?

Front-loaded with the core action and well organized, but it is dense to the point of over-specification. The anecdotal passage ('RNV's #00b0a0 was blended in paint; the same ingredients at the same weights in lab give #9cc1a5, 15.94 away...') is illustrative but longer than needed to make the paint-vs-lab 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?

An output schema exists, so return values need not be explained (though the description notes 'Returns hex and rgb' anyway). Between format handling, weight defaults, six documented modes, collision rules ('Brand names win over CSS names on collision'), and read-only guarantees, an agent has everything required 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 description coverage is 0%, so the description must compensate, and it does thoroughly: it enumerates accepted color formats (hex, CSS name, RNV brand name, palette reference with the 'Spring line:2' index syntax), explains that weights are optional integers defaulting to equal, and defines all six mode values with their physical models.

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?

Opens with a specific verb and resource: 'Blend up to 12 colors into one.' It explicitly distinguishes itself from siblings in the closing sentence ('to convert one color between formats use convert_color, and to measure how far apart two colors are use color_difference'), so an agent can route correctly without opening any 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?

Gives explicit when-to-use guidance for the mode parameter ('Reach for paint when BLENDING brand colors into a new one, and lab when SAMPLING between them') and names two alternatives (convert_color, color_difference) with the conditions that select them. Nothing is left to inference.

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