Overlay one image on top of another (e.g., add watermark, logo). Uses PIL for precise positioning - no AI needed.
AI agents use compose_images to create or update resources in Fal Ai MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Fal Ai MCP Server environment.
The tool creates a new composite image by overlaying images, which is a write operation that modifies or creates data. It is reversible (the output can be regenerated or discarded). Severity is medium because misuse could result in watermarking or obscuring images unexpectedly, but the blast radius is limited to image modification rather than system-level or destructive consequences.
From the tool's definition Tool description states it 'overlay one image on top of another' and 'add watermark, logo', which involves modifying an image by creating a composite output. This is a creation/modification operation without deletion.
Documented attack patterns abuse exactly the kind of access compose_images gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and Fal Ai MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for compose_images:
{
"version": "1",
"default": "deny",
"tools": {
"compose_images": {
"limits": [
{
"counter": "compose_images_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}compose_images 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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Overlay one image on top of another (e.g., add watermark, logo). Uses PIL for precise positioning - no AI needed. It is categorised as a Write tool in the Fal Ai MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the Fal Ai MCP Server MCP server in PolicyLayer and add a rule for compose_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 Fal Ai MCP Server. Nothing to install.
compose_images 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 compose_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 compose_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.
compose_images is provided by the Fal Ai MCP Server MCP server (luminarylane/fal-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 18 Fal Ai MCP Server tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
18 Fal Ai MCP Server tools catalogued and risk-classified — across an index of 42,500+ MCP servers.