join_team · AT MCP: Risk & Policy

WHAT IT DOES

What join_team does on ATMcp

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

WHY IT NEEDS A POLICY

Why join_team needs a policy

The tool creates or modifies team membership state by adding an agent to a team using a join token. This is reversible (agents can leave teams), produces persistent side effects in a shared multi-agent system, and affects downstream operations (agent can now access team resources, participate in task distribution).

From the tool's definition Tool name 'join_team' and context of team-based multi-agent system indicates creating or modifying organizational state. Description states 'Join (or re-join) a team' which involves writing membership data to a distributed system.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

join_team Rate-limited

join_team 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": {
    "join_team": {
      "limits": [
        {
          "counter": "join_team_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

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PolicyLayer is an MCP gateway: every tool call is checked against your rule before it reaches ATMcp, so you can run agents against it safely.

FAQ

Questions about join_team

What does the join_team tool do? +

Join (or re-join) a team. The join token may be passed here or sent as an. It is categorised as a Write tool in the ATMcp MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on join_team? +

Register the AT MCP server in PolicyLayer and add a rule for join_team: 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 ATMcp. Nothing to install.

What risk level is join_team? +

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

Can I rate-limit join_team? +

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

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

join_team is provided by the AT MCP server (midcheck/atmcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.