MatchReplace · Fledgling MCP: Risk & Policy

WHAT IT DOES

What MatchReplace does on Fledgling

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

WHY IT NEEDS A POLICY

Why MatchReplace needs a policy

An AI agent can call MatchReplace faster than any human can review — one bad instruction and it creates or modifies resources in Fledgling by the hundred, each call as confident as the last.

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

MatchReplace Rate-limited

MatchReplace 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": {
    "MatchReplace": {
      "limits": [
        {
          "counter": "matchreplace_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 Fledgling, so you can run agents against it safely.

FAQ

Questions about MatchReplace

What does the MatchReplace tool do? +

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

How do I enforce a policy on MatchReplace? +

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

What risk level is MatchReplace? +

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

Can I rate-limit MatchReplace? +

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

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

MatchReplace is provided by the Fledgling MCP server (teaguesterling/fledgling). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.