design_check_contrast

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

With no annotations, the description carries the full burden, and it does disclose the return contract: ratio, AA/AAA pass status, and remediation suggestions on failure — meaningful because no output schema exists. It stops short of saying the tool is purely read-only/no-side-effect or which WCAG thresholds/version apply, but the 'Check … Returns' framing makes the non-mutating nature clear enough.

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 front-loaded sentences with zero filler: the first says what it does, the second what comes back. Nothing is repeated from the schema or wasted.

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 two-parameter pure-computation tool with no output schema, the description supplies the return shape an agent needs and names the standards (AA/AAA). The only meaningful gap is disambiguation from the sibling contrast tools, which is a usage concern rather than missing invocation detail.

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?

Both parameters are fully documented in the schema (100% coverage) as hex foreground and background colors, and the description adds nothing beyond that. Baseline 3 is appropriate when the schema already does the parameter work.

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 and resource ('Check WCAG contrast ratio between two colors'), plus the outputs it produces. However, it never distinguishes itself from the close siblings design_check_palette_contrast and design_suggest_accessible_color, so an agent must guess which of the three contrast tools applies.

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?

Usage is only implied by 'between two colors' — the reader infers this is the single-pair check rather than the palette-wide variant. There is no explicit when-to-use, no alternative named, and no exclusion relative to design_check_palette_contrast or design_suggest_accessible_color.

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