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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false. The description adds valuable context with 'Pure offline math' and details the computation: 'computes the smallest foreground adjustment (and an alternative background adjustment) that reaches AA/AAA — with the achieved ratio and direction.' No contradiction; it supplements the annotation hints well.

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?

Three dense sentences, each earning its place. The first sentence states purpose and algorithm, the second describes outputs, and the third connects to audit_contrast and alternative approaches. No fluff or redundancy.

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 tool with nested object parameters and no output schema, the description covers input context (failing pairs), behavior (online math, minimal adjustments), and output characteristics (achieved ratio and direction). It stops short of fully specifying the output object structure, but the combination of schema and this description is sufficient for an agent to 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 baseline is 3. The description reinforces that inputs are 'failing' pairs and mentions 'target ratio'/'level', but it does not add significant meaning beyond what the schema's own parameter descriptions already provide. The added value is minimal.

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 explicitly states the tool's function: 'Given failing WCAG color pairs, return the MINIMAL color change that clears the target ratio.' This is a specific verb+resource+outcome. It also references the sibling tool audit_contrast, distinguishing it as the remediation counterpart to the audit 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 provides clear when-to-use guidance by stating 'Feeds directly from audit_contrast's failing pairs: pass them here to get concrete passing values instead of brute-forcing colors by hand.' This names an alternative (manual brute-forcing) and the intended workflow, though it does not explicitly list when-not-to-use scenarios.

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