compose_images · MCP Nano Banana MCP: Risk & Policy

WHAT IT DOES

What compose_images does on MCP Nano Banana

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

WHY IT NEEDS A POLICY

Why compose_images needs a policy

This tool creates new image data by compositing multiple input images, making it a Write operation. It does not retrieve or query existing data (Read), execute arbitrary code or system commands (Execute), irreversibly delete data (Destructive), or move money (Financial).

From the tool's definition The tool description states it will "Combine multiple images into a new composition," which creates a new image asset. This is a generative write operation that produces new data (composite images) from input sources.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

compose_images Rate-limited

compose_images 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": {
    "compose_images": {
      "limits": [
        {
          "counter": "compose_images_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 MCP Nano Banana, so you can run agents against it safely.

FAQ

Questions about compose_images

What does the compose_images tool do? +

Combine multiple images into a new composition. nano-banana supports up to 3 input images. nano-banana-pro supports up to 14 input images (up to 5 humans, 6 objects). Great for: - Product mockups - Fashion photos (dress on model) - Creative collages - Style transfer from multiple references. It is categorised as a Write tool in the MCP Nano Banana MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on compose_images? +

Register the MCP Nano Banana MCP server in PolicyLayer and add a rule for compose_images: 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 MCP Nano Banana. Nothing to install.

What risk level is compose_images? +

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

Can I rate-limit compose_images? +

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

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

compose_images is provided by the MCP Nano Banana MCP server (pgarciapg/mcp-nano-banana). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.