add_edge · Flowchart MCP: Risk & Policy

WHAT IT DOES

What add_edge does on Flowchart MCP

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

WHY IT NEEDS A POLICY

Why add_edge needs a policy

add_edge creates a new connection in a flowchart diagram, which is a reversible modification operation. This falls squarely within the Write category (create/modify data). The severity is low because adding an edge has minimal blast radius—it only affects the visual structure of a diagram and can be easily removed. No destructive, executable, or financial consequences.

From the tool's definition Tool description states 'Add a directed edge (connection) between two nodes.' This is a creation operation that modifies the flowchart structure reversibly. The sibling tools include 'remove_edge', indicating edges can be undone.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

add_edge Rate-limited

add_edge 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": {
    "add_edge": {
      "limits": [
        {
          "counter": "add_edge_rate",
          "window": "minute",
          "max": 30,
          "scope": "grant"
        }
      ]
    }
  }
}

LIMIT THIS TOOL →

Instant setup, no code required.

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

FAQ

Questions about add_edge

What does the add_edge tool do? +

Add a directed edge (connection) between two nodes. It is categorised as a Write tool in the Flowchart MCP MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on add_edge? +

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

What risk level is add_edge? +

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

Can I rate-limit add_edge? +

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

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

add_edge is provided by the Flowchart MCP server (zafer-liu/flowchart_mcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.