matrix_invite_user

THE RISK

Medium Risk

Why matrix_invite_user needs a policy

Inviting a user to a room creates a new membership record/invitation in the Matrix protocol. This is a reversible write operation (the invitation can be rescinded or the user can be removed). Misuse could spam users with unwanted invitations, hence medium severity.

From the tool's definition Invite a user to a room

Documented attack patterns abuse exactly the kind of access matrix_invite_user gives an agent:

POLICY

How to control matrix_invite_user

PolicyLayer is an MCP gateway — it sits between your AI agents and Crow, and nothing reaches the server without passing your rules. This is the rule we recommend for matrix_invite_user:

policy.json

{
  "version": "1",
  "default": "deny",
  "tools": {
    "matrix_invite_user": {
      "limits": [
        {
          "counter": "matrix_invite_user_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

matrix_invite_user 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.

Create a free account and register Crow — nothing to install.
Add this policy — paste it, or build it visually.
Point your MCP client (Claude, Cursor, anything) at your gateway URL.

LIMIT THIS TOOL →

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EXPLORE

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Go deeper

The MCP Attack Database → Documented attack patterns against MCP deployments — and the policies that stop them.
Argument validation → Checking tool call arguments against schema and policy before they run.
Scoped token → Per-person credentials that grant a defined subset of servers and tools.
Rate Limiting MCP Tool Calls: A Practical Guide →
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FAQ

Questions about matrix_invite_user

What does the matrix_invite_user tool do? +

Invite a user to a room. Rate-limited: 10/hour. It is categorised as a Write tool in the Crow MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on matrix_invite_user? +

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

What risk level is matrix_invite_user? +

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

Can I rate-limit matrix_invite_user? +

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

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

matrix_invite_user is provided by the Crow MCP server (kh0pper/crow). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every Crow tool call.

Start from Crow, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

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