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

Annotations only provide readOnlyHint, so the description carries the behavioral burden and handles it thoroughly. It discloses CIEDE2000 matching, hex_collision behavior, null returns for near-neutral hues, the member_source_caveat, and the label_placement_basis caveat, plus the 'silence is honest' policy. No contradiction with readOnlyHint exists.

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 dense and long, but almost every clause earns its place by explaining caveats and historical provenance. It is front-loaded with the core purpose, though the single-paragraph structure makes it harder to parse than a short purpose sentence plus explicit caveats would be.

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?

For a historically nuanced tool, the description is unusually complete: it explains the source, the matching algorithm, the null behavior, provenance caveats, and the key difference from hay_contrast. With an output schema present, return-value documentation is not the description's responsibility, and nothing an agent needs to call this correctly appears to be missing.

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%, and both parameters are documented in the schema itself. The description adds context about output objects and matching behavior, but it does not materially enrich the meaning of the input parameters 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?

The description states a specific verb and resource: it snaps an input hex to Vanderpoel hue-family labels and returns documented dyad/triad groupings from specific build artifacts. It also distinguishes itself from hay_contrast by explicitly saying it carries NO proportional ratio, so an agent can tell it apart from related tools.

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 clearly implies when this is appropriate — when Vanderpoel's categorical 'good' groupings are needed — and explicitly contrasts with hay_contrast. It also documents null-return conditions, but it does not provide a direct 'use this instead of X' routing beyond the one mention of hay_contrast, nor does it address the many colour-harmony siblings.

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