scan_accessibility · OverlayQA MCP: Risk & Policy

WHAT IT DOES

What scan_accessibility does on OverlayQA MCP

AI agents invoke scan_accessibility to trigger actions in OverlayQA MCP. What it does depends on the arguments the agent supplies, and its effects often reach beyond the immediate call — builds kicked off, notifications sent, workflows started.

WHY IT NEEDS A POLICY

Why scan_accessibility needs a policy

The tool actively executes an audit process against an external URL, making outbound requests and running analysis logic. This is more than a passive read — it triggers an external operation whose effects depend on the target URL argument. It is not destructive or financial, but it does consume rate-limited quota (3 scans/day on free plans), confirming it performs a real external action.

From the tool's definition "Run an accessibility audit on a URL" — triggers an external scan/audit operation against a remote URL; "Scans one page per call" confirms it performs an active external operation rather than simply retrieving static data.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

scan_accessibility Rate-limited

scan_accessibility stays usable, but rate-capped — a runaway agent can't fire it dozens of times a minute. Everything else on the server is denied unless you say otherwise.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "scan_accessibility": {
      "limits": [
        {
          "counter": "scan_accessibility_rate",
          "window": "minute",
          "max": 10,
          "scope": "grant"
        }
      ]
    }
  }
}

RATE-LIMIT THIS TOOL →

Instant setup, no code required.

PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches OverlayQA MCP, so you can run agents against it safely.

FAQ

Questions about scan_accessibility

What does the scan_accessibility tool do? +

Run an accessibility audit on a URL. Returns WCAG violations with severity, descriptions, and an overall score. Scans one page per call. Free plans include 3 scans per day; Pro is unlimited. It is categorised as a Execute tool in the OverlayQA MCP MCP Server, which means it can trigger actions or run processes. Use rate limits and argument validation.

How do I enforce a policy on scan_accessibility? +

Register the OverlayQA MCP server in PolicyLayer and add a rule for scan_accessibility: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches OverlayQA MCP. Nothing to install.

What risk level is scan_accessibility? +

scan_accessibility is a Execute tool with high risk. Execute tools should be rate-limited and have argument validation enabled.

Can I rate-limit scan_accessibility? +

Yes. Add a rate_limit block to the scan_accessibility rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.

How do I block scan_accessibility completely? +

Set action: deny in the PolicyLayer policy for scan_accessibility. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.

What MCP server provides scan_accessibility? +

scan_accessibility is provided by the OverlayQA MCP server (overlayqa/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.