build_chart · AI Charts MCP: Risk & Policy

WHAT IT DOES

What build_chart does on AI Charts

AI agents use build_chart 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 build_chart needs a policy

This tool creates/constructs a chart by adding nodes and edges, which is a reversible write operation. It creates new data structures (diagrams) without executing code or deleting anything. Severity is medium because an AI agent could misuse it to create large or malformed diagrams, but the blast radius is limited to the diagramming application.

From the tool's definition Build a chart with nodes and edges. Nodes use temp_ids that edges reference.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

build_chart Rate-limited

build_chart 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": {
    "build_chart": {
      "limits": [
        {
          "counter": "build_chart_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 build_chart

What does the build_chart tool do? +

Build a chart with nodes and edges. Nodes use temp_ids that edges reference. 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 build_chart? +

Register the AI Charts MCP server in PolicyLayer and add a rule for build_chart: 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 build_chart? +

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

Can I rate-limit build_chart? +

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

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

build_chart 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.