set_active_repl · Replit MCP Server MCP: Risk & Policy

WHAT IT DOES

What set_active_repl does on Replit MCP Server

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

WHY IT NEEDS A POLICY

Why set_active_repl needs a policy

This tool modifies application state (the 'active' repl context) reversibly. While it doesn't directly create or delete data, it changes configuration that affects how subsequent file operations behave. This is a write-class action because it persistently alters the operational state of the user's session.

From the tool's definition Tool description states it 'Set[s] the active repl ID for subsequent file operations' — this modifies the operational state of the MCP session by changing which repl context subsequent operations target.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

set_active_repl Rate-limited

set_active_repl 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": {
    "set_active_repl": {
      "limits": [
        {
          "counter": "set_active_repl_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 Replit MCP Server, so you can run agents against it safely.

FAQ

Questions about set_active_repl

What does the set_active_repl tool do? +

Set the active repl ID for subsequent file operations. It is categorised as a Write tool in the Replit MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on set_active_repl? +

Register the Replit MCP Server MCP server in PolicyLayer and add a rule for set_active_repl: 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 Replit MCP Server. Nothing to install.

What risk level is set_active_repl? +

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

Can I rate-limit set_active_repl? +

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

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

set_active_repl is provided by the Replit MCP Server MCP server (nova-3951/replit-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.