add_node · AI Charts MCP: Risk & Policy

WHAT IT DOES

What add_node does on AI Charts

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

WHY IT NEEDS A POLICY

Why add_node needs a policy

Adding a node creates/modifies chart data reversibly. It does not execute code, destroy data, or move money. It is clearly Write rather than Execute because it manipulates a known data structure (a diagram) with predictable, bounded effects. The severity is low because misuse would only affect the target chart's structure, causing no damage beyond visual/informational consequence.

From the tool's definition Tool name 'add_node' and description 'Add a single node to a chart' — creates a new diagram element reversibly. This is a data creation operation without side effects beyond the chart structure itself.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

add_node Rate-limited

add_node 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_node": {
      "limits": [
        {
          "counter": "add_node_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 AI Charts, so you can run agents against it safely.

FAQ

Questions about add_node

What does the add_node tool do? +

Add a single node to a chart. Width/height optional — omit for auto-size. It is categorised as a Write tool in the AI Charts 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_node? +

Register the AI Charts MCP server in PolicyLayer and add a rule for add_node: 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 AI Charts. Nothing to install.

What risk level is add_node? +

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

Can I rate-limit add_node? +

Yes. Add a rate_limit block to the add_node 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_node completely? +

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

add_node is provided by the AI Charts MCP server (tjameswilliams/ai-charts). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.