update_mock · Postman MCP: Risk & Policy

WHAT IT DOES

What update_mock does on Postman

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

WHY IT NEEDS A POLICY

Why update_mock needs a policy

This tool modifies an existing mock server rather than creating new ones or destructively removing them. Updates are typically reversible through subsequent updates, and the scope appears limited to mock server configuration rather than production systems or destructive operations. The impact could affect testing workflows, justifying medium severity.

From the tool's definition Tool name 'update_mock' and description 'Update an existing mock server' indicate modification of existing data (mock server configuration) in a reversible manner.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

update_mock Rate-limited

update_mock 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": {
    "update_mock": {
      "limits": [
        {
          "counter": "update_mock_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

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

FAQ

Questions about update_mock

What does the update_mock tool do? +

Update an existing mock server. It is categorised as a Write tool in the Postman MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on update_mock? +

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

What risk level is update_mock? +

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

Can I rate-limit update_mock? +

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

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

update_mock is provided by the Postman MCP server (postmanv3/postman-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.