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

Annotations declare readOnlyHint=true, which the description does not contradict and actually supports by describing a read-style retrieval. The description adds rich behavioral context by listing the exact domains of information returned (colour science, archive anchor, provenance, physics, cultural reading) and stating its canonical/single-call nature, exceeding what annotations alone convey.

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 logically structured: opening definition, content enumeration, usage instruction, and examples. It is somewhat verbose but each sentence adds productive detail (e.g., specific examples). The length is justified by the tool's comprehensive nature, though it could be tightened without losing 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?

Despite the tool's high complexity, the description gives a thorough overview of the returned data and its role in the tool ecosystem. Since an output schema exists and the description outlines the major return categories, it provides enough context for an agent to select and invoke the tool appropriately. The examples clarify input expectations and output anchoring.

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 100%, so the baseline is 3. The description does not add significant parameter-level meaning beyond the schema; it only includes example hex values which are illustrative but not semantically additive. The description mentions the equivalent of parameters (hex values) but does not clarify the other fields, though the schema already handles that.

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 states a specific verb ('Returns') and resource ('everything known about a hex value'), enumerating the exact categories of data. It clearly distinguishes itself from siblings by declaring it the canonical foundation call and explicitly naming the tools it replaces (colour_dna, archive_provenance, etc.), making its scope and role unmistakable.

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 explicitly says to 'Use this as the foundation call when you need the complete picture' and contrasts it with chaining multiple separate tools, naming those alternatives. This gives clear when-to-use guidance and identifies the alternative approach for more granular needs.

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