sed_edit · MCP SmallEdit MCP: Risk & Policy

WHAT IT DOES

What sed_edit does on MCP SmallEdit

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

WHY IT NEEDS A POLICY

Why sed_edit needs a policy

The tool modifies file content through sed pattern matching and replacements. While these changes are reversible (files can be restored via list_backups/restore_backup functions available on the server), the tool creates or alters data, classifying it as Write rather than Read.

From the tool's definition Tool description states 'Make small edits to files' and 'pattern replacements, and simple text transformations' — these are direct modifications to file content.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

sed_edit Rate-limited

sed_edit 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": {
    "sed_edit": {
      "limits": [
        {
          "counter": "sed_edit_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 SmallEdit, so you can run agents against it safely.

FAQ

Questions about sed_edit

What does the sed_edit tool do? +

Make small edits to files using sed patterns. Efficient for single-line changes, pattern replacements, and simple text transformations. It is categorised as a Write tool in the MCP SmallEdit MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on sed_edit? +

Register the MCP SmallEdit MCP server in PolicyLayer and add a rule for sed_edit: 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 SmallEdit. Nothing to install.

What risk level is sed_edit? +

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

Can I rate-limit sed_edit? +

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

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

sed_edit is provided by the MCP SmallEdit MCP server (mikeybeez/mcp-smalledit). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.