desktop_add_shape

THE RISK

Medium Risk

Why desktop_add_shape needs a policy

This tool creates or modifies 3D scene objects within a WebAR project file. It is reversible (shapes can be removed or modified later), involves no code execution, and poses no deletion or financial risk. However, it can alter project state and affect rendered experiences, warranting 'medium' severity. Confidence is high but not absolute due to lack of detail about permission boundaries or validation strictness.

From the tool's definition Tool name 'add' and description 'Add a 3D shape' indicate creation/modification. Target is '.expanse.json', a project configuration file. The phrase 'with proper 8th Wall validation' confirms structural changes to project state.

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

POLICY

How to control desktop_add_shape

PolicyLayer is an MCP gateway — it sits between your AI agents and 8th Wall MCP Server, and nothing reaches the server without passing your rules. This is the rule we recommend for desktop_add_shape:

policy.json

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

desktop_add_shape 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 8th Wall MCP 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 8th Wall MCP Server tools

Destructive desktop_remove_component Remove a custom component from the project Destructive project_delete_file Delete a file under PROJECT_ROOT Execute devserver_start Start a static file server for PROJECT_ROOT Execute devserver_stop Stop the static file server Execute generate_custom_javascript ⚠️ WEB PROJECTS ONLY - NOT FOR DESKTOP! Generate A-Frame components for web-based projects Write assets_download_url Download a file by URL into project/assets/ Write apply_experience_template Apply a pre-configured AR experience template. This automatically sets up components, code Write assets_unzip Unzip a .zip file into project assets directory

All 64 8th Wall MCP Server tools →

Write tools on other servers

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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 desktop_add_shape

What does the desktop_add_shape tool do? +

Add a 3D shape to .expanse.json with proper 8th Wall validation. It is categorised as a Write tool in the 8th Wall MCP 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 desktop_add_shape? +

Register the 8th Wall MCP Server MCP server in PolicyLayer and add a rule for desktop_add_shape: 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 8th Wall MCP Server. Nothing to install.

What risk level is desktop_add_shape? +

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

Can I rate-limit desktop_add_shape? +

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

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

desktop_add_shape is provided by the 8th Wall MCP Server MCP server (superdwayne/8thwallmcp). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.

Enforce policy on every 8th Wall MCP Server tool call.

Start from 8th Wall MCP Server, add the rest of your stack, and see everything your agents can call. Then put policy on all of it.

CHECK YOUR STACK →