contrast_check

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

Describes output and accepted input formats. No annotations provided, so description carries full burden. Does not explicitly state it is read-only, but behavior is transparent regarding what it returns.

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, no wasted words. First sentence states purpose and output, second adds input formats and usage hint. Front-loaded with key information.

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?

Given simple parameters, output schema exists (though not shown), and description covers input formats, output details, and usage context. Complete for a straightforward tool.

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 0% but description adds significant meaning: both parameters accept hex, CSS name, RNV brand name, or saved-palette reference. This compensates fully for missing schema descriptions.

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?

Clearly states the tool checks WCAG contrast ratio between foreground and background colors for accessibility. Specifies output includes ratio and pass/fail for AA/AAA. Distinguishes from sibling tools like color_difference by focusing on accessibility.

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?

Explicitly tells when to use: 'Use this to check if text will be readable on a background.' Does not mention when not to use or alternative tools, but the purpose is clear enough.

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