AI agents use swap_face to create or update resources in Midjourney MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Midjourney MCP Server environment.
Face swapping creates a new modified image by combining facial features from two source images. This is a Write operation as it produces a new artifact (the face-swapped image) without irreversibly destroying the originals. Severity is medium because face swapping can be misused for non-consensual image manipulation or deepfakes, but the action itself is reversible and the originals remain intact.
From the tool's definition Swap faces between two images
Documented attack patterns abuse exactly the kind of access swap_face gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Midjourney MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for swap_face:
{
"version": "1",
"default": "deny",
"tools": {
"swap_face": {
"limits": [
{
"counter": "swap_face_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}swap_face stays usable, but capped — an agent stuck in a loop can't make hundreds of changes a minute. Everything else on the server is denied unless you say otherwise.
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Swap faces between two images. It is categorised as a Write tool in the Midjourney MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Midjourney MCP Server MCP server in PolicyLayer and add a rule for swap_face: 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 Midjourney MCP Server. Nothing to install.
swap_face is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.
Yes. Add a rate_limit block to the swap_face 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 swap_face. 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.
swap_face is provided by the Midjourney MCP Server MCP server (z23cc/midjourney-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from Midjourney MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.
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7 Midjourney MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.