createMessenger

Creates a messenger. You can optionally specify an Id for the messenger, if not provided one will be generated.

SERVERFusionauth SOURCE@fusionauth/mcp-api

Medium RISK CLASS

Category Write

Parameters 00 required

Recommended Rate-limitedsee the rule below

Registry record Grade F, identity unverified Pull the record →

This record as markdown: /tools/io-fusionauth-mcp-api/createmessenger.md

WHAT IT DOES

What createMessenger does on Fusionauth

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

RISK

Why createMessenger is rated Medium

Creating a messenger is a reversible data modification operation. It adds a new resource to the system but does not execute arbitrary code, delete data irreversibly, or involve financial transactions.

From the tool's definition Tool description explicitly states it "Creates a messenger," which is a write operation that generates or persists new data. The optional Id parameter indicates the tool creates a new resource that will be stored in the FusionAuth system.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs createMessenger safely

PolicyLayer is an MCP gateway: it sits between your AI agents and Fusionauth, and checks every tool call against a rule you set before the call runs. Nothing changes on the server itself. For createMessenger, this is the rule to start with:

createMessenger Rate-limited

createMessenger 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": {
    "createMessenger": {
      "limits": [
        {
          "counter": "createmessenger_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL → Instant setup, no code required.

The button opens the PolicyLayer dashboard: create your workspace, connect Fusionauth, apply this rule, and every createMessenger call is checked against it from then on.

FAQ

Questions about createMessenger

What does the createMessenger tool do? +

Creates a messenger. You can optionally specify an Id for the messenger, if not provided one will be generated. It is categorised as a Write tool in the Fusionauth MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on createMessenger? +

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

What risk level is createMessenger? +

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

Can I rate-limit createMessenger? +

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

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

createMessenger is provided by the Fusionauth MCP server (@fusionauth/mcp-api). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

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