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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is covered. The description still adds real behavioral context: the output matches Coolours' own Export feature, names match the Coolours UI, and the 'use the output as given' instruction warns against post-processing. It does not cover limits or failure modes (e.g. what happens with unsupported colour input), so not a 5.

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?

What the tool does is front-loaded in the first sentence, followed by the sibling routing and a usage caveat. Four short sentences with almost no filler; the final caveat sentence is slightly redundant with the earlier 'matches Coolours' Export feature' claim.

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-value details are correctly omitted. Combined with the annotations, the description covers format choice, naming behavior, sibling disambiguation, and a consumption caveat — everything an agent needs to call 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?

Schema coverage is 50%: `colours` is documented in the schema, while `format` is only an enum with no description. The description supplies the meaning of the two format values (CSS custom properties vs JavaScript object), which compensates for part of the gap, but it says nothing about the input colour formats or the 20-item limit beyond what the schema already states.

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 (Export) plus resource (palette) plus the two concrete output forms (CSS custom properties / JavaScript object), and it names the differentiating behavior — each colour named after its nearest named colour. An agent can distinguish it from create_palette_link and parse_palette_link from the text alone.

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: 'create_palette_link already returns the CSS; use this for the JS object, or for a palette you didn't create.' That is a named alternative plus the precise conditions that select this tool over it.

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