pick_color

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

Describes behavioral traits: samples composited truth, not computed styles; includes WCAG contrast verdict; explains 'at' parameter behavior (top-left vs center). Lacks mention of side effects or performance implications, but as a read-only sampling tool it is sufficiently transparent.

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?

Description is front-loaded with main purpose and usage tips. Each sentence adds value, though it could be slightly more concise. Structured well for an AI agent to parse quickly.

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 no output schema, the description covers what the tool returns (composited truth, computed color/background, WCAG contrast) and how to use parameters. Adequate for understanding the tool's functionality and output.

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 value by explaining the difference between center and top-left sampling, and implicitly suggests using uid/selector or coordinates. Adds context beyond 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?

The description clearly states the tool samples the actual painted pixel, gives composited truth, computed colors, and WCAG contrast. It distinguishes from sibling tools like explain_styles and annotated_screenshot by focusing on exact pixel color and 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?

Explicitly states when to use: 'the color looks off', 'is this the exact brand hex?', 'is this text readable on that background?'. Provides guidance on using 'at:top-left' for pure background and suggests explain_styles for finding which rule set a wrong color.

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