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

Beyond the readOnlyHint annotation, the description discloses important behavioral details: the returned result already carries rendered palette downloads (PNG, PDF, ASE, JSON, CSS) and should be shown to the customer. It also warns specifically against presenting archive-derived anchors as recommended colours and mandates palette_finalize for any agent-chosen palette. These are valuable behaviors not inferable from the annotation alone.

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 front-loaded with the core purpose, immediately explains the sibling distinction, and then gives terse but necessary behavioral instructions. Every sentence earns its place: the result-display note, the warning about archive anchors, and the palette_finalize handoff all contribute to correct agent behavior. Nothing is redundant.

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 single-parameter tool with an output schema and read-only annotation, the description is remarkably complete. It covers selection criteria, expected return artifacts, customer-facing display steps, and a critical correctness caveat about recommended colours. No essential guidance 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?

The input schema fully documents the single required 'hex' parameter with a concrete example, so the schema already carries the semantic load. The description adds only that it fingerprints a single hex colour, which is consistent but does not materially extend parameter understanding. Baseline 3 is appropriate for full schema coverage.

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 precisely that this tool produces a compact semantic fingerprint for a single hex colour, and it explicitly distinguishes itself from colour_passport as one component of that broader tool. It further clarifies when to use it, saying to use it only when the user wants the fingerprint format alone. This gives an agent a clear, unambiguous reason to select it over its siblings.

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 explicit routing guidance: use colour_passport for a general colour profile, and use colour_dna only when the user explicitly requests the fingerprint format alone. It also provides follow-up instruction to call palette_finalize if the agent constructs its own final palette. This fully covers when and when not to use the tool.

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