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

Annotations only provide readOnlyHint=true; the description adds the 20-value limit, automatic deduplication, and the list of return components (colour science, archive anchor, evidence grade, etc.), going well beyond the annotation. This gives the agent important behavioral context for a batch operation.

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?

Two sentences with zero filler. The first sentence front-loads the batch nature and input limit; the second adds use cases. Every word earns its place.

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 moderate complexity and presence of an output schema, the description covers invocation limits, return contents, and use cases. It's complete enough for an agent to select and call the tool correctly without additional context.

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 is 3. The description enhances parameter semantics by noting the 'up to 20 hex values' limit and 'deduplicates hex values automatically', which add constraints not present in the schema for the hexes parameter.

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 explicitly states it's the 'Batch version of colour_passport' and says it submits up to 20 hex values and returns a full Colour Passport for each, clearly distinguishing it from the singular sibling tool. The verb 'lookup' and 'returns' make the action and resource 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?

Provides explicit usage guidance: 'Use for multi-colour workflows, Figma palette analysis, or any case where calling colour_passport separately for each colour would be slow.' It names the alternative (colour_passport) and implies single-colour lookups should use that instead.

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