cancel_flow

THE RISK

Critical Risk

Why cancel_flow needs a policy

Cancelling a flow execution is an irreversible action — a cancelled flow cannot be resumed or restarted from the same point. This permanently terminates the execution state, making it Destructive. The blast radius is high because cancelling a business-critical flow (e.g., an approval workflow, incident escalation, or change management process) can leave processes in an inconsistent or unrecoverable state.

From the tool's definition Cancel a running or paused flow execution by its context ID

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

POLICY

How to control cancel_flow

PolicyLayer is an MCP gateway — it sits between your AI agents and Now Sdk Ext, and nothing reaches the server without passing your rules. This is the rule we recommend for cancel_flow:

policy.json

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

cancel_flow 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 Now Sdk Ext — 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 Now Sdk Ext tools

Destructive query_delete_records Find records matching an encoded query and delete them all. Execute aggregate_grouped Run aggregate functions (COUNT, AVG, MIN, MAX, SUM) grouped by a field on any Execute execute_action Execute a ServiceNow Flow Designer action by scoped name. Execute execute_flow Execute a published ServiceNow Flow Designer flow by scoped name. Execute execute_script Execute JavaScript on a ServiceNow instance using Scripts - Background Execute execute_subflow Execute a ServiceNow Flow Designer subflow by scoped name. Execute run_atf_test Execute a single ServiceNow ATF (Automated Test Framework) test by its sys_id. Execute run_atf_test_suite Execute a ServiceNow ATF test suite and wait for all tests to complete.

All 86 Now Sdk Ext 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 Now Sdk Ext → 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_flow

What does the cancel_flow tool do? +

Cancel a running or paused flow execution by its context ID. It is categorised as a Destructive tool in the Now Sdk Ext 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_flow? +

Register the Now Sdk Ext MCP server in PolicyLayer and add a rule for cancel_flow: 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 Now Sdk Ext. Nothing to install.

What risk level is cancel_flow? +

cancel_flow 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_flow? +

Yes. Add a rate_limit block to the cancel_flow 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_flow completely? +

Set action: deny in the PolicyLayer policy for cancel_flow. 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_flow? +

cancel_flow is provided by the Now Sdk Ext MCP server (sonisoft-cnanda/now-sdk-ext-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Now Sdk Ext tool call.

Start from Now Sdk Ext, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →