Evaluates UI elements for accessibility issues that automated scanners miss. COST: $0.01 USDC via x402 on Base-compatible EVM network per call. Checks beyond what axe/Lighthouse/WAVE catch at the design stage: - Touch targets below 24×24px (WCAG 2.5.8 AA hard fail) - Touch targets below 44×44px (...
Risk signalsHigh parameter count (19 properties)
Part of the Axcess — Design Accessibility Evaluation server.
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AI agents call evaluate_accessibility to retrieve information from Axcess — Design Accessibility Evaluation without modifying any data. This is common in research, monitoring, and reporting workflows where the agent needs context before taking action. Because read operations don't change state, they are generally safe to allow without restrictions -- but you may still want rate limits to control API costs.
Even though evaluate_accessibility only reads data, uncontrolled read access can leak sensitive information or rack up API costs. An agent caught in a retry loop could make thousands of calls per minute. A rate limit gives you a safety net without blocking legitimate use.
Read-only tools are safe to allow by default. No rate limit needed unless you want to control costs.
{
"version": "1",
"default": "deny",
"tools": {
"evaluate_accessibility": {}
}
}See the full Axcess — Design Accessibility Evaluation policy for all 3 tools.
These attack patterns abuse exactly the kind of access evaluate_accessibility gives an agent. Each links to the full case and the policy that stops it:
Other read tools across the catalogue. The same approach applies to each: allow, with a rate cap to control cost.
Evaluates UI elements for accessibility issues that automated scanners miss. COST: $0.01 USDC via x402 on Base-compatible EVM network per call. Checks beyond what axe/Lighthouse/WAVE catch at the design stage: - Touch targets below 24×24px (WCAG 2.5.8 AA hard fail) - Touch targets below 44×44px (WCAG 2.5.5 AAA recommended) - Information conveyed by color alone without a secondary indicator (WCAG 1.4.1) - Missing focus indicators on interactive elements (WCAG 2.4.7) - Focus rings thinner than 2px (WCAG 2.4.11) - Focus ring contrast below 3:1 against adjacent background (WCAG 2.4.11) - Interactive elements below the practical usability height floor Args: - elements: Array of 1–50 UI element objects - screen_name: Optional label for the evaluation report Each element requires: element_type. Provide width_px/height_px for touch target checks. Provide uses_color_only + secondary indicator flags for 1.4.1 checks. Provide is_interactive + focus_visible + focus indicator properties for focus checks. Returns: Structured report with: - Per-element scores (0–100) and specific issues - Severity levels (critical/major/minor) with WCAG references - What automated tools miss and why - Concrete fix recommendations - Overall score and verdict (pass/needs_work/fail) - Top issues sorted by severity. It is categorised as a Read tool in the Axcess — Design Accessibility Evaluation MCP Server, which means it retrieves data without modifying state.
Register the Axcess — Design Accessibility Evaluation MCP server in PolicyLayer and add a rule for evaluate_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 Axcess — Design Accessibility Evaluation. Nothing to install.
evaluate_accessibility is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the evaluate_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.
Set action: deny in the PolicyLayer policy for evaluate_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.
evaluate_accessibility is provided by the Axcess — Design Accessibility Evaluation MCP server (https://axcess-mcp-server.fly.dev/mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 3 Axcess — Design Accessibility Evaluation tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
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