build_config · Terragrunt MCP Server MCP: Risk & Policy

WHAT IT DOES

What build_config does on Terragrunt MCP Server

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

WHY IT NEEDS A POLICY

Why build_config needs a policy

The tool explicitly writes configuration files to disk. While this is reversible in principle (files can be deleted or overwritten), writing infrastructure-as-code configuration files carries high severity because misconfigured Terragrunt HCL files (remote state backends, provider configs, dependency blocks) could lead to infrastructure misconfigurations, data exposure, or unintended resource management when applied.

From the tool's definition 'Generate or write Terragrunt HCL configuration files (terragrunt.hcl)'

Attacks that exploit this kind of access

Recommended rule Ready

Verdict

build_config Rate-limited

build_config 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": {
    "build_config": {
      "limits": [
        {
          "counter": "build_config_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 Terragrunt MCP Server, so you can run agents against it safely.

FAQ

Questions about build_config

What does the build_config tool do? +

Generate or write Terragrunt HCL configuration files (terragrunt.hcl). Use cases: remote_state backends (S3, GCS, Azure), provider generation, dependency blocks, hooks, and inputs. It is categorised as a Write tool in the Terragrunt MCP Server MCP Server, which means it can create or modify data. Consider rate limits to prevent runaway writes.

How do I enforce a policy on build_config? +

Register the Terragrunt MCP Server MCP server in PolicyLayer and add a rule for build_config: 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 Terragrunt MCP Server. Nothing to install.

What risk level is build_config? +

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

Can I rate-limit build_config? +

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

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

build_config is provided by the Terragrunt MCP Server MCP server (omattsson/terragrunt-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.