create_source · Paymongo MCP: Risk & Policy

WHAT IT DOES

What create_source does on Paymongo

AI agents use create_source to create or update resources in Paymongo — usually the action step of a workflow, after the agent has gathered context. Every call changes real data in your Paymongo environment.

WHY IT NEEDS A POLICY

Why create_source needs a policy

This tool creates a new payment source object in the PayMongo system, which is a Write operation (creates data reversibly). While payment-related, it does not directly move money or commit financial obligations—it only creates a source/method for future payments. However, given the financial context (PayMongo is a payment gateway) and that misuse could initiate unauthorized payment flows, severity is high.

From the tool's definition Tool name 'create_source' and description 'Create a GCash/GrabPay payment source' indicate data creation. The return of 'a redirect checkout URL' confirms a reversible write operation that creates a new payment source record.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

create_source Rate-limited

create_source 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.

View as policy code

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "create_source": {
      "limits": [
        {
          "counter": "create_source_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

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PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches Paymongo, so you can run agents against it safely.

FAQ

Questions about create_source

What does the create_source tool do? +

Create a GCash/GrabPay payment source (returns a redirect checkout URL). It is categorised as a Write tool in the Paymongo MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on create_source? +

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

What risk level is create_source? +

create_source is a Write tool with medium risk. Write tools should be rate-limited to prevent accidental bulk modifications.

Can I rate-limit create_source? +

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

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

create_source is provided by the Paymongo MCP server (theyahia/paymongo-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.