Lint markup against the specification

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

Annotations already declare readOnlyHint=true and openWorldHint=false, so safety is covered. The description adds genuinely useful context beyond the annotations: the checks are scoped to shipping failures and the result is explicitly advisory, not a certification of accessibility — important for how the agent should phrase findings. It stops short of describing result format or coverage limits.

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?

Front-loaded with the verb and resource, then a tight enumeration of concrete failure types, closed by a one-clause caveat. The long list is informative rather than padding — it defines the check surface with no redundant sentences.

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 lint tool with fully documented parameters, the description covers purpose, scope, and the crucial advisory semantics. The one gap is the return shape: there is no output schema and the description never indicates what a result contains (findings list? per-check messages?), which the agent would need to present results.

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 both markup (with its size bound) and componentId are already documented in the schema. The description adds nothing about the parameters themselves, so the 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?

Specific verb ('Checks') plus concrete resource ('HTML or CSS') and an enumerated set of failure classes (accessible names, tabindex, focus outlines, live regions), so the agent knows exactly what linting surface this covers. It does not explicitly distinguish itself from the sibling check_contrast, which overlaps on the colour/dark-mode checks, so it falls short of a 5.

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?

Usage is implied by the check list ('the failures that actually ship'), but there is no explicit when-to-use statement and no routing to alternatives such as check_contrast for pure contrast questions or get_component for spec lookups. The advisory caveat addresses interpretation of results, not tool selection.

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