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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=true, so an agent understands this is a safe read operation via open-world network access. The description adds useful context: it reads markup only and cannot test contrast, focus order, or script-built widgets, which explains why it operates this way. It does not describe fetch failures or rate limits, but it goes beyond the annotations.

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?

Two sentences, front-loaded with the verb and scope, then the checklist, then the limitations. Every clause carries information; nothing is redundant.

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?

Because there is no output schema, the description implies the return format: an issue list where each issue names a WCAG 2.2 criterion; the schema documents compareUrl's diff semantics. This is nearly complete, but it lacks any detail on response shape or how many issues are returned.

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% and all three parameters are documented in the schema, including compareUrl's fixed/new/remaining semantics. The description adds no syntax or format details, which is acceptable but no more than 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?

The description gives a specific verb (audit), a specific scope (one page's static HTML), and an enumerated list of issues the tool detects (missing lang or title, images without alt, heading jumps, tabindex above zero, and so on). The scope 'one page' alone distinguishes it from audit_site_accessibility, so an agent can select 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?

The description states the scope clearly, and by ruling out contrast, focus order, and script-built widgets it lets an agent understand when other tools are appropriate. However, it never names an alternative (check_contrast, plan_focus_order, audit_site_accessibility) explicitly, so the routing must be inferred.

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