Compare two images pixel-by-pixel and identify visual differences. Returns structured diff data including: - Overall diff percentage and pixel counts - Clusters of different regions with bounding box coordinates (x, y, width, height) - Severity rating per cluster (trivial/minor/moderate/major) - ...
AI agents call get_diff_of_images to retrieve information from Playwright Stealth without modifying anything — typically the context-gathering step in research, monitoring, and reporting workflows, before the agent takes action elsewhere.
This tool performs image analysis and comparison, which is a retrieval and query operation. It produces no side effects—no data is created, modified, deleted, or overwritten. It does not execute arbitrary code or external operations beyond internal image processing. The output is purely informational (diff data and heatmap paths).
From the tool's definition Tool compares two images pixel-by-pixel and returns structured diff data including diff percentage, pixel counts, bounding box coordinates, severity ratings, and heatmap file paths.
Documented attack patterns abuse exactly the kind of access get_diff_of_images gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Playwright Stealth, and nothing reaches the server without passing your rules. This is the rule we recommend for get_diff_of_images:
{
"version": "1",
"default": "deny",
"tools": {
"get_diff_of_images": {}
}
}get_diff_of_images is read-only, so it stays allowed — but everything else on the server is denied unless you say otherwise.
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Compare two images pixel-by-pixel and identify visual differences. Returns structured diff data including: - Overall diff percentage and pixel counts - Clusters of different regions with bounding box coordinates (x, y, width, height) - Severity rating per cluster (trivial/minor/moderate/major) - Clustering metadata with the gap used and suggestions for tuning - File paths to generated heatmap images showing diff intensity Clustering: By default, nearby diff regions are automatically grouped using a natural-breaks algorithm that finds the optimal merge distance. This produces a manageable number of clusters where each represents a distinct problem area. To override, set cluster_gap explicitly (0 = no merging, or a specific pixel distance). Heatmap output: A PNG image where diff regions are colored from yellow (subtle difference) to red (major difference). A composite version overlays this on the source image for easy comparison. Use cases: - Compare a design mock screenshot against actual UI implementation - Compare a Figma mock of a single component against a full-page screenshot (auto-aligned) - Detect visual regressions between two versions of a page - Verify CSS/layout changes only affect intended areas Requirements: - Images must be accessible as local file paths - Images can have different dimensions — the smaller image is automatically aligned within the larger one using template matching Note: Anti-aliased pixels (font smoothing, rounded corners) are excluded by default to reduce false positives. Set include_aa=true to include them. It is categorised as a Read tool in the Playwright Stealth MCP Server, which means it retrieves data without modifying state.
Register the Playwright Stealth MCP server in PolicyLayer and add a rule for get_diff_of_images: 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 Playwright Stealth. Nothing to install.
get_diff_of_images 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 get_diff_of_images 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 get_diff_of_images. 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.
get_diff_of_images is provided by the Playwright Stealth MCP server (pulsemcp/mcp-servers). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Playwright Stealth, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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68 Playwright Stealth tools catalogued and risk-classified — across an index of 43,000+ MCP servers.