check_contrast

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

With no annotations, the description does the heavy lifting. It reveals that the tool can operate on single pairs or scan tokens, uses multiple algorithms, and that threshold only affects scan mode. It does not describe return format, error handling, or performance, but the core behavior is transparent and consistent with expected contrast checking.

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 two sentences, immediately conveying the purpose and modes. No unnecessary words. Information density is high and front-loaded.

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 5 parameters, no output schema, and no annotations, the description covers the essential modes and parameters. It might lack details on return values or error cases, but for a straightforward check tool, it is adequate for an agent to decide and invoke 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 coverage is 100%, providing baseline 3. The description adds semantic value by explaining the two interaction modes: background+foreground for a single check vs. threshold+pathPrefix for scanning. It also clarifies that 'threshold' only applies to scan mode. This exceeds the schema's basic existence 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?

The description clearly states that the tool checks color contrast using WCAG 2.1 and APCA algorithms. It outlines two distinct modes (single pair or token scan), which differentiates it from sibling tools that handle tokens, themes, or audits. The verb 'check' and resource 'contrast' are specific and unambiguous.

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 provides clear context on when to use the tool (checking contrast) and explains the two modes. It does not explicitly state when NOT to use it or list alternatives, but since no sibling tool performs contrast checking, the guidance is sufficient. The scan mode usage is partially implied via parameter hints.

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