insert_sibling · Ast Editor MCP: Risk & Policy

WHAT IT DOES

What insert_sibling does on Ast Editor

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

WHY IT NEEDS A POLICY

Why insert_sibling needs a policy

The tool inserts a new sibling node into an AST, which creates or modifies code reversibly. This is a Write operation (structural modification without deletion or execution). Severity is medium because incorrect insertions could break code syntax or introduce bugs, but the change is reversible via undo/deletion.

From the tool's definition Tool name 'insert_sibling' combined with server's stated purpose of 'structural edits' and sibling tools like 'add_field', 'add_method', 'add_parameter', 'add_top_level' — all of which create or modify code structures reversibly.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

insert_sibling Rate-limited

insert_sibling 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": {
    "insert_sibling": {
      "limits": [
        {
          "counter": "insert_sibling_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 Ast Editor, so you can run agents against it safely.

FAQ

Questions about insert_sibling

What does the insert_sibling tool do? +

insert_sibling. It is categorised as a Write tool in the Ast Editor MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on insert_sibling? +

Register the Ast Editor MCP server in PolicyLayer and add a rule for insert_sibling: 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 Ast Editor. Nothing to install.

What risk level is insert_sibling? +

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

Can I rate-limit insert_sibling? +

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

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

insert_sibling is provided by the Ast Editor MCP server (kambleakash0/ast-editor). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.