Download an image from a URL and save it to a file.
AI agents use download_image to create or update resources in ComfyUI MCP Server — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your ComfyUI MCP Server environment.
This tool fetches an image from a URL and writes it to the local filesystem. While it has a read component (fetching from URL), the primary action is writing/saving a file to disk, making 'Write' the appropriate category. Misuse could involve saving malicious content or overwriting existing files, warranting medium severity.
From the tool's definition 'Download an image from a URL and save it to a file'
Documented attack patterns abuse exactly the kind of access download_image gives an agent:
PolicyLayer is an MCP gateway — it sits between your AI agents and ComfyUI MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for download_image:
{
"version": "1",
"default": "deny",
"tools": {
"download_image": {
"limits": [
{
"counter": "download_image_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}download_image 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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Download an image from a URL and save it to a file. It is categorised as a Write tool in the ComfyUI MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.
Register the ComfyUI MCP Server MCP server in PolicyLayer and add a rule for download_image: 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 ComfyUI MCP Server. Nothing to install.
download_image 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 download_image 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 download_image. 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.
download_image is provided by the ComfyUI MCP Server MCP server (overseer66/comfyui-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Start from ComfyUI 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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4 ComfyUI MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.