a11y_validate

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

No annotations are provided, so the description carries the full burden. It does well: it discloses that the tool is read-only in effect (a check/compute that needs no API key), names the two algorithms, and describes the return content (contrast ratio, pass/fail for normal and large text, suggested fixes). It does not mention error handling for malformed hex, which is the main remaining gap.

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?

Three short, front-loaded lines: purpose first, then the cost/auth note, then the return shape. Every sentence earns its place and nothing is padded.

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?

There is no output schema, but the description explicitly enumerates the return values, so an agent knows what to expect from a four-parameter computation tool. Only edge-case/error behavior is unspecified, a minor omission.

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 the schema already documents foreground/background hex, fontSize pixels, and the algorithm enum. The description only alludes to large-text thresholds and algorithm choice, adding no syntax or format detail beyond the schema. Baseline 3 applies.

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 (Check) and a precisely scoped resource (one foreground/background color pair) and names the standards covered (WCAG 2.1 and APCA). The 'one ... pair' scoping cleanly distinguishes it from the sibling pitch_audit_contrast, which implies bulk auditing.

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 phrase 'Check one foreground and background color pair' implies the single-pair use case, and 'FREE - No API key required' gives a practical prerequisite. There is no explicit guidance on when to prefer this over pitch_audit_contrast or which algorithm enum value to choose for a given situation.

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