AI agents use set_defaults 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.
The tool modifies system or user preferences ('set_defaults') rather than reading or executing arbitrary code. This is reversible configuration change typical of Write operations. Severity is medium because misconfigured defaults could affect multiple jobs or workflows, but the impact is correctable.
From the tool's definition Tool name 'set_defaults' indicates modification of configuration or default values. Sibling tools include get_defaults, suggesting this tool writes/updates defaults that affect subsequent operations.
Documented attack patterns abuse exactly the kind of access set_defaults 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 set_defaults:
{
"version": "1",
"default": "deny",
"tools": {
"set_defaults": {
"limits": [
{
"counter": "set_defaults_rate",
"window": "minute",
"max": 30,
"scope": "grant"
}
]
}
}
}set_defaults 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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set_defaults. 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 set_defaults: 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.
set_defaults 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 set_defaults 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 set_defaults. 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.
set_defaults is provided by the ComfyUI MCP Server MCP server (joenorton/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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15 ComfyUI MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.