// MCP TOOL REFERENCE

cancel_job

ServerComfyUI MCP Server
CategoryDestructive

WHAT IT DOES

What cancel_job does on ComfyUI MCP Server

AI agents call cancel_job to permanently remove resources in ComfyUI MCP Server — typically in cleanup and lifecycle workflows. It does its job in a single call, and there is no undo.

THE RISK

Critical Risk

Why cancel_job needs a policy

Cancelling a job is an irreversible action — once a running or queued job is cancelled, the in-progress computation is terminated and cannot be resumed. This is not merely a write/update but an action that permanently stops execution. The blast radius is medium since it affects ongoing jobs (potentially wasting compute or user work) but does not delete stored assets or data.

From the tool's definition Cancel a queued or running job... Can cancel jobs that are queued or currently running.

Documented attack patterns abuse exactly the kind of access cancel_job gives an agent:

POLICY

How to control cancel_job

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 cancel_job:

policy.json

{
  "version": "1",
  "default": "deny",
  "hide": [
    "cancel_job"
  ]
}

cancel_job disappears from the agent's tool list entirely, and any attempt to call it is denied. The rest of the server keeps working.

Create a free account and register ComfyUI MCP Server — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

RESTRICT THIS TOOL →

Free to start. No card required.

EXPLORE

Related tools and policies

More ComfyUI MCP Server tools

Execute run_workflow run_workflow Execute regenerate regenerate Write publish_asset publish_asset Write set_comfyui_output_root set_comfyui_output_root Write set_defaults set_defaults Read get_asset_metadata Get full metadata and provenance for a generated asset. Returns comprehen Read get_defaults Get current effective defaults for image, audio, and video generation. Re Read get_job get_job

All 15 ComfyUI MCP Server tools →

Destructive tools on other servers

Android Forensics ADB MCP Server create_full_backup 0xarchive web3_revoke_key Frida Game Hacking MCP clear_scan cPanel MCP Server clear_spam_box

Go deeper

Critical-risk tools in ComfyUI MCP Server → Every critical-risk tool this server exposes, in one view.
All critical-risk MCP tools → Every critical-risk tool across the catalogue, and the policy pattern that contains them.
The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Blast radius → How much damage one compromised or confused agent can do — and how to bound it.
Tool call approval → Approval gates on individual tool calls: auto-allow, prompt, or deny.
Rate Limiting MCP Tool Calls: A Practical Guide →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about cancel_job

What does the cancel_job tool do? +

Cancel a queued or running job. Allows the AI to cancel jobs that are no longer needed, providing user control and resource management. Can cancel jobs that are queued or currently running. Args: prompt_id: The prompt ID to cancel (from workflow submission) Returns: Dict with cancellation status. It is categorised as a Destructive tool in the ComfyUI MCP Server MCP Server, which means it can permanently delete or destroy data. Block by default and require explicit approval.

How do I enforce a policy on cancel_job? +

Register the ComfyUI MCP Server MCP server in PolicyLayer and add a rule for cancel_job: 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.

What risk level is cancel_job? +

cancel_job is a Destructive tool with critical risk. Critical-risk tools should be blocked by default and only enabled with explicit human approval.

Can I rate-limit cancel_job? +

Yes. Add a rate_limit block to the cancel_job 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.

How do I block cancel_job completely? +

Set action: deny in the PolicyLayer policy for cancel_job. 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.

What MCP server provides cancel_job? +

cancel_job 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.

Enforce policy on every ComfyUI MCP Server tool call.

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.

CHECK YOUR STACK →

Free to start. No card required.

15 ComfyUI MCP Server tools catalogued and risk-classified — across an index of 43,000+ MCP servers.