stk_push

THE RISK

Critical Risk

Why stk_push needs a policy

This tool initiates an M-Pesa STK (SIM Toolkit) push payment request, which directly triggers a financial transaction on a customer's mobile device. It involves moving real money via Safaricom's M-Pesa service. Misuse could result in unauthorized payment requests being sent to customers, making this a critical financial risk.

From the tool's definition Prompts the customer to authorize a payment on their mobile device

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

POLICY

How to control stk_push

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

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "stk_push": {
      "deny_if": [
        {
          "conditions": [],
          "on_deny": "Requires human approval."
        }
      ]
    }
  }
}

Any call to stk_push is blocked until a human approves it. The rest of the server keeps working.

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

GATE THIS TOOL →

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EXPLORE

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Go deeper

Critical-risk tools in Daraja MCP → 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.
Human-in-the-loop → When a tool call should wait for a person — and when policy can decide alone.
Tool call approval → Approval gates on individual tool calls: auto-allow, prompt, or deny.
How to Add Spending Controls to Any MCP Agent →
Rate Limiting MCP Tool Calls: A Practical Guide →

FAQ

Questions about stk_push

What does the stk_push tool do? +

Prompts the customer to authorize a payment on their mobile device. It is categorised as a Financial tool in the Daraja MCP MCP Server, which means it involves financial transactions. Block by default and require explicit approval.

How do I enforce a policy on stk_push? +

Register the Daraja MCP server in PolicyLayer and add a rule for stk_push: 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 Daraja MCP. Nothing to install.

What risk level is stk_push? +

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

Can I rate-limit stk_push? +

Yes. Add a rate_limit block to the stk_push 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 stk_push completely? +

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

stk_push is provided by the Daraja MCP server (jameskanyiri/darajamcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Daraja MCP tool call.

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

CHECK YOUR STACK →