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

The annotation already indicates read-only behavior, and the description does not contradict it. The description adds valuable context by specifying what the narrative contains (history, civilisations, archive names) and provides a concrete example. It does not discuss potential latencies or edge cases, but the output schema and read-only hint lower the burden.

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 three sentences: what it does, when to use it, and an example. It is concise, front-loaded with the core purpose, and every sentence earns its place. No fluff or redundancy.

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 presence of a complete input schema, an output schema, and a read-only annotation, the description needs only to convey the tool's purpose and when to use it. It does so effectively, including a rich example. There is no significant missing information for a tool of this moderate complexity.

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?

The input schema has 100% description coverage for both parameters, so the baseline is 3. The description does not add much beyond the schema—it repeats the hex requirement via the example but does not elaborate on n_archives or how it affects the output. The schema already documents the parameters adequately, and the description adds minimal additional value here.

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 uses a specific verb ('returns') and clearly identifies the resource and scope ('cultural story of a colour'), describing exactly what the tool does. It also distinguishes this from siblings like colour_timeline or colour_dna by focusing on the narrative and historical journey. The concrete example reinforces the purpose.

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 gives clear use cases ('image generation prompts, brand storytelling, and creative briefs') which indicate when to apply the tool. However, it does not explicitly state when not to use it or mention alternative tools for other colour-related analyses, so it falls short of a 5 but provides clear context.

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