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

Annotations already declare readOnlyHint=true and openWorldHint=false, and the description adds value beyond them by disclosing the return shape: violations grouped by severity with node ids. This is genuinely useful since there is no output schema, though auth/rate-limit behavior is still unstated.

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?

One tightly packed sentence with zero waste: scope first, then checked categories, then return format. Nothing could be removed without losing signal.

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 read-only audit tool with full schema coverage and no output schema, the brief return description plus enumerated check categories is nearly sufficient. Only the missing 'when not to use this' guidance and any default-fallback nuance (page_home, AA) keep it from a 5.

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 all four parameters (including the A/AA/AAA enum and the id-vs-templateSlug exclusion) are already documented. The description adds no format or default detail beyond the schema, which is the expected baseline.

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?

Names a specific verb+resource ('WCAG audit of a site or template page') and enumerates exactly what is checked (contrast, alt text, headings, ARIA, interactive elements), which clearly distinguishes it from the sibling audit_seo. An agent can pick it without opening the schema.

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?

Scope is implied through 'site or template page' and the schema's mutual exclusion of id/templateSlug, but the description never says when to choose this over audit_seo or what prerequisites exist. Usage is inferable rather than stated.

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