private_streamable_start · Claude Imagine MCP: Risk & Policy

WHAT IT DOES

What private_streamable_start does on Claude Imagine

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

WHY IT NEEDS A POLICY

Why private_streamable_start needs a policy

This tool writes HTML content into a browser DOM element in real-time via WebSocket. It modifies the UI state by injecting or replacing content, which is a reversible write operation. No code execution, deletion, or financial action is implied. Severity is medium because arbitrary HTML injection could include scripts or malicious markup if misused, but the primary action is a content write.

From the tool's definition 'Start streaming HTML content to an element' — creates/modifies DOM content by streaming HTML into a target element

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

private_streamable_start Rate-limited

private_streamable_start 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": {
    "private_streamable_start": {
      "limits": [
        {
          "counter": "private_streamable_start_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 Claude Imagine, so you can run agents against it safely.

FAQ

Questions about private_streamable_start

What does the private_streamable_start tool do? +

Start streaming HTML content to an element. It is categorised as a Write tool in the Claude Imagine MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on private_streamable_start? +

Register the Claude Imagine MCP server in PolicyLayer and add a rule for private_streamable_start: 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 Claude Imagine. Nothing to install.

What risk level is private_streamable_start? +

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

Can I rate-limit private_streamable_start? +

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

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

private_streamable_start is provided by the Claude Imagine MCP server (t3rm1nu55/claudeimagine). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.