Check Contrast

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

Annotations declare readOnlyHint=true, idempotentHint=true, openWorldHint=false, and destructiveHint=false, so safety and purity are already understood. The description contributes the WCAG levels and non-text scope but doesn't cover output format or edge-case behavior beyond the schema. This is acceptable given annotation coverage.

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?

Single, efficient sentence that front-loads the core action and constraint. No filler or repetition.

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, idempotent contrast-check tool with full schema coverage and clear annotations, the description is largely sufficient. However, missing explicit output information or guidance on handling transparent colors (for which the base parameter exists) leaves a minor gap.

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 baseline is 3. The description adds the concept of WCAG levels but the schema already documents all three parameters (foreground, background, base). No extra semantics such as default blending rules are provided beyond what's in the schema.

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?

States a specific verb (Check) and resource (WCAG contrast ratio between foreground and background colors), and clarifies the standards evaluated (AA, AAA, non-text). This clearly distinguishes it from siblings like colors_difference or colors_batch_contrast.

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?

Usable for assessing accessibility, but the description gives no explicit when-to-use versus alternatives or when-not-to-use guidance. It also doesn't clarify the difference from colors_batch_contrast, which is a missed opportunity given the sibling list.

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