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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description adds meaningful behavioral context: it returns a pass/warn/fail verdict with the numbers behind it, and explains that ramp=true skips pairwise separation. This goes beyond the annotations without contradicting them.

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?

Two sentences with zero waste. The core purpose and the key behavioral detail (ramp=true) are front-loaded, and the return format is stated compactly. Every sentence earns its place.

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 read-only audit tool with 100% schema coverage and no output schema, the description is nearly complete. It explains what checks are performed, the return verdict, and the ramp option. The only minor gap is that it doesn't describe the exact structure of the returned numbers, but since there's no output schema, a bit more detail on the return format could help. Still, the description is sufficient for an agent to select and invoke the tool correctly.

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 schema already documents all three parameters (colors, ramp, background). The description adds value by explaining the semantic effect of ramp=true (skips pairwise separation) and clarifying that colors are in slot order, but it doesn't add syntax details beyond what the schema provides. Baseline 3 is appropriate.

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 ('Audit') and resource ('existing chart colors'), and enumerates the exact accessibility checks performed (OKLab separation under five vision conditions, WCAG 2.2 non-text contrast). This clearly distinguishes it from sibling tools like build_ramp or solve_palette, which create or optimize palettes rather than audit them.

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 context for when to use the tool: auditing existing chart colors for accessibility. It also explains the ramp=true option for sequential/diverging scales, which is a usage condition. However, it doesn't explicitly name sibling alternatives or state when NOT to use this tool (e.g., when building a new palette, use build_ramp or solve_palette instead).

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