create_session

Server Repl takafu/repl-mcp

Category Write

Risk class Medium

Parameters 00 required

WHAT IT DOES

What create_session does on Repl

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

WHY IT NEEDS A POLICY

Why create_session needs a policy

An AI agent can call create_session faster than any human can review — one bad instruction and it creates or modifies resources in Repl by the hundred, each call as confident as the last.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

create_session Rate-limited

create_session 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_session": {
      "limits": [
        {
          "counter": "create_session_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 Repl, so you can run agents against it safely.

FAQ

Questions about create_session

What does the create_session tool do? +

Create a new REPL session with preset or custom configuration. Use displayName to set a custom name that appears in the browser tab title. Returns a webUrl - you MUST display this URL to the user or open it in a browser. Note: If using zsh in custom commands, you may need to manually run. It is categorised as a Write tool in the Repl 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_session? +

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

What risk level is create_session? +

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

Can I rate-limit create_session? +

Yes. Add a rate_limit block to the create_session 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_session completely? +

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

create_session is provided by the Repl MCP server (takafu/repl-mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.