check_contrast

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

With no annotations and no output schema, the description carries the transparency burden itself. It does disclose the core behavior—computing a contrast ratio between two colors—but it does not state the return format, whether it evaluates WCAG compliance, or how it handles invalid or non-hex colors. This is adequate for a simple pure calculation but leaves the output contract implicit.

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 a single, front-loaded sentence with no filler. Every word adds semantic value, and it is appropriately sized for a two-parameter utility tool.

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 simple two-parameter tool, the description plus schema is sufficient for invoking it correctly with two hex colors. However, the absence of an output schema and any mention of the return value or WCAG interpretation leaves a meaningful gap for an agent trying to use the result 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%, with foreground and background each documented as color hex values. The tool description adds no additional parameter semantics beyond what the schema already provides, so the baseline score of 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 clearly states a specific operation ('check color contrast ratio') and scopes it to exactly two colors, which distinguishes it from broader sibling tools like color_check_all or audit_accessibility. This is not a tautology: it adds the 'ratio between two colors' detail beyond the tool name. The purpose is immediately clear to an agent.

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 no guidance about when to use this tool versus alternatives such as color_check_all, get_selection_colors, audit_accessibility, or generate_a11y_report. There is no mention of prerequisites, expected input context, or cases where a broader audit tool would be more appropriate.

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