createUserWithId

Creates a user. You can optionally specify an Id for the user, 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/createuserwithid.md

WHAT IT DOES

What createUserWithId does on Fusionauth

AI agents use createUserWithId 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 createUserWithId is rated Medium

Creating users is a write operation that reversibly modifies data. Severity is high because user creation in an identity provider can impact access control, authentication flows, and system security if misused (e.g., creating unauthorized admin accounts or privilege escalation). However, it is not destructive (reversible via deletion), not financial, and not code execution.

From the tool's definition Tool description states it 'Creates a user' with optional custom ID specification. This is a create operation that modifies the FusionAuth database by adding a new user record.

Attacks that exploit this kind of access

RECOMMENDED RULE

The rule that runs createUserWithId 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 createUserWithId, this is the rule to start with:

createUserWithId Rate-limited

createUserWithId 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": {
    "createUserWithId": {
      "limits": [
        {
          "counter": "createuserwithid_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 createUserWithId call is checked against it from then on.

FAQ

Questions about createUserWithId

What does the createUserWithId tool do? +

Creates a user. You can optionally specify an Id for the user, 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 createUserWithId? +

Register the Fusionauth MCP server in PolicyLayer and add a rule for createUserWithId: 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 createUserWithId? +

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

Can I rate-limit createUserWithId? +

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

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

createUserWithId 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.

KEEP EXPLORING

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