add_field · Ast Editor MCP: Risk & Policy

WHAT IT DOES

What add_field does on Ast Editor

AI agents use add_field 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 add_field needs a policy

This tool creates or modifies code by adding a field to a data structure or class definition. While reversible (can be undone by deleting), it modifies source code with potential downstream effects on build, type checking, and dependent code. Classified as Write rather than Execute because it directly edits AST structures rather than running code.

From the tool's definition Tool name 'add_field' combined with server description indicating 'structural edits' and sibling tools like 'add_import', 'add_method', 'add_parameter', 'add_top_level' that create/modify code structures.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

add_field Rate-limited

add_field 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": {
    "add_field": {
      "limits": [
        {
          "counter": "add_field_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 add_field

What does the add_field tool do? +

add_field. 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 add_field? +

Register the Ast Editor MCP server in PolicyLayer and add a rule for add_field: 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 add_field? +

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

Can I rate-limit add_field? +

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

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

add_field 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.