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Verify an accessibility fix

verify_fix

Read-onlyIdempotent

Re-scan a fixed element after you apply an accessibility change to get a machine-checked pass or fail confirming the violation is gone or still present.

Instructions

Re-scan a specific element after applying an accessibility fix and confirm the violation is gone. After you edit the code and serve it (deployed, staging, or http://localhost:3000), call this with the URL and the selector you fixed to get a machine-checked verified: true|false (DOM engines only — visual_audit findings are out of scope). Pass the WCAG criterion (e.g. "1.1.1") or axe rule id (e.g. "color-contrast") to check just that criterion; omit it to require the element be clean of ALL violations. A blocked page (bot-challenge / HTTP error) is reported as unverified, never a pass — verification fails closed. verified: true is only returned when the selector matched at least one element AND the criterion is one the DOM engines check; if the selector matches no element the result is verified: false with reason "not-found" ("selector matched no elements"), a criterion outside the coverage set returns reason "not-verifiable" ("not checked by any WebAbility tool"); a finding in scope that only the AI judge can settle, when the judge did not run or gave no verdict, also returns "not-verifiable", and shadow-DOM (>>>) / iframe selectors return "unsupported-selector" — pass the element's current selector, or re-run scan_page if your fix removed the element. Pair with scan_page → generate_ai_fix → verify_fix for a full find-fix-verify cycle.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "url": "<url>",
      "selector": "<selector>"
    },
    "name": "verify_fix"
  }
}

Input Schema

Name	Required	Description
`url`	Yes	URL now serving the fix (deployed, staging, or http://localhost:3000). Also accepted as `page` or `pageUrl`.
`wcag`	No	Optional: WCAG criterion (e.g. "1.1.1", "1.4.3") or axe rule id (e.g. "color-contrast") to verify specifically. Omit to require the element be free of ALL violations.
`selector`	Yes	CSS selector of the element you fixed — use the `selector` from the original scan_page issue
`viewport`	No	Viewport size (default: desktop). Use the same viewport the issue was found at.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedv1.7.0Oct 5, 2026

changedInput schema / properties / url / description

Previous value: -"URL now serving the fix (deployed, staging, or http://localhost:3000)"New value: +"URL now serving the fix (deployed, staging, or http://localhost:3000). Also accepted as `page` or `pageUrl`."

First observedv1.3.1Jul 11, 2026

TDQS

A4.8/5.0

Behavior5/5

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

Beyond readOnlyHint/idempotentHint, it discloses the fail-closed behavior for blocked pages, the exact reason codes returned (not-found, not-verifiable, unsupported-selector), and the two preconditions for verified: true. This is exactly the extra context annotations cannot carry.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Front-loaded with purpose, then behavior, then edge cases, then workflow. Dense and slightly run-on in the reason-code enumeration, but nearly every clause carries distinct information; nothing is padding.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

No output schema exists, so the description has to explain return values, and it does: the verified: true|false shape plus each failure reason and its message. Combined with annotations and full schema coverage, an agent has everything needed to call and interpret it.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100%, so baseline is 3; the description still adds the operational meaning of the wcag parameter (omit to require clean of ALL violations) and ties selector to the original scan_page issue. It does not mention the viewport-matching guidance that the schema provides, but that is already covered.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb and resource ('Re-scan a specific element after applying an accessibility fix and confirm the violation is gone') and explicitly scopes out visual_audit findings. An agent can distinguish it from scan_page or visual_audit 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.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Gives concrete preconditions (edit the code, serve it at deployed/staging/localhost), names the alternative to omit ('visual_audit findings are out of scope'), and prescribes the sequence 'scan_page → generate_ai_fix → verify_fix'. It also says to re-run scan_page if the fix removed the element.

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