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

Annotations declare readOnlyHint and openWorldHint, so the safety profile is covered. The description adds some value by listing the computed metrics, but doesn't say anything about determinism or precision limits.

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?

One dense sentence front-loaded with the verb and the main metric, then the ancillary outputs. Efficient, though the comma-heavy enumeration is slightly hard to parse.

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?

A pure computation tool with readOnly annotation, full schema coverage, and no output schema. The description adequately covers inputs, outputs, and safety context; only the verdict thresholds and contrast definition are left unstated.

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% and both parameters already carry rich format examples (hex, rgb, hsl, oklch, names, Tailwind), so the schema fully documents them. The description adds nothing beyond the names 'first'/'second'. Baseline 3.

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?

Specific verb (Compare) and resource (two colors), and the description enumerates the outputs (CIEDE2000, deltaE OK, verdict, lightness/chroma/hue shifts, contrast) that distinguish it from siblings like check_contrast or convert_color.

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?

Implies usage by enumerating what it computes, but never states when to call this instead of the sibling check_contrast or nearest_names. No explicit alternatives or exclusions are given.

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