new_from_mermaid

THE RISK

Medium Risk

Why new_from_mermaid needs a policy

This tool creates a new BPMN diagram (a write/create operation) from Mermaid code and sets it as the current working context. It is reversible since diagrams can be deleted or replaced. No code execution, data deletion, or financial action is involved.

From the tool's definition 'Create a new BPMN diagram from Mermaid code and set it as current context'

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

POLICY

How to control new_from_mermaid

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

policy.json

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

new_from_mermaid 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 MCP-BPMN Server — 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 →

Free to start. No card required.

EXPLORE

Related tools and policies

More MCP-BPMN Server tools

Destructive bpmn_delete_diagram Delete a saved BPMN diagram file Destructive bpmn_delete_element Delete an element from the process Destructive delete_diagram_file Delete a saved BPMN diagram file Destructive delete_element Delete an element from the current diagram Write new_bpmn Create a new BPMN diagram and set it as current context Write add_activity Add an activity to the current diagram Write add_event Add an event to the current diagram Write add_gateway Add a gateway to the current diagram

All 41 MCP-BPMN Server tools →

Write tools on other servers

M-Team MCP Server download_torrent YouTube MCP Server generate_video_title Android Forensics ADB MCP Server combine_reports 0xarchive web3_signup

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 →
MCP Security: Why Prompt Guardrails Aren't Enough →

FAQ

Questions about new_from_mermaid

What does the new_from_mermaid tool do? +

Create a new BPMN diagram from Mermaid code and set it as current context. It is categorised as a Write tool in the MCP-BPMN Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on new_from_mermaid? +

Register the MCP-BPMN Server MCP server in PolicyLayer and add a rule for new_from_mermaid: 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 MCP-BPMN Server. Nothing to install.

What risk level is new_from_mermaid? +

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

Can I rate-limit new_from_mermaid? +

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

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

new_from_mermaid is provided by the MCP-BPMN Server MCP server (oisee/mcp-bpmn). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every MCP-BPMN Server tool call.

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

CHECK YOUR STACK →