Font Colour Advisor

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

Annotations already declare readOnlyHint=true, so the description adds value by detailing the output: ranked list, WCAG grades, and specific recommendations for body text, large text, and UI components. It provides behavioral context beyond the annotation, making the tool's non-destructive nature clear.

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 sentence of about 25 words, front-loaded with input context. Every word earns its place, with no redundancy or filler.

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 the tool's simplicity (2 required parameters, 100% schema coverage, output schema present), the description adequately covers input and output behavior. No additional details about edge cases or errors are necessary for a focused analysis 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 100%, so the baseline is 3. The description rephrases parameter names ('background hex', 'palette of candidate foreground colours') without adding new semantic meaning beyond the schema. It does not clarify formatting or units beyond what the schema provides.

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 the tool's purpose: ranking foreground colours against a background hex using contrast ratios and WCAG grades, with specific recommendations for body text, large text, and UI components. It distinguishes itself from sibling colour tools by focusing on font/foreground contrast advice.

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 implies usage when needing contrast recommendations for foreground colours, but does not explicitly state when to use this tool versus alternatives like 'accessibility_check' or other colour comparison tools. No exclusion criteria or alternative references are provided.

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