diff --git a/app.json b/app.json
index 8e567fd..f07e071 100644
--- a/app.json
+++ b/app.json
@@ -15,6 +15,10 @@
         "STDIO_MODE_ONLY": {
             "description": "Only allow tool requests via STDIO mode?",
             "value": "false"
+        },
+        "USE_TEMP_DIR": {
+           "description": "If True, gems are installed in an isolated temporary directory and will not affect or reuse the user's ~/.gem folder. Not a secure sandbox.",
+            "value": "false"
         }
     },
     "formation": [
diff --git a/example_clients/test_sse.py b/example_clients/test_sse.py
index 0b531d8..6149707 100644
--- a/example_clients/test_sse.py
+++ b/example_clients/test_sse.py
@@ -32,8 +32,14 @@ def mcp(method_name, args=None):
 
     Examples:
         python example_clients/test_sse.py mcp list_tools
-        python example_clients/test_sse.py mcp call_tool --args '{"name": "fetch_webpage_and_markdownify", "arguments": {"url": "https://example.com"}}'
-    """
+
+        python example_clients/test_sse.py mcp call_tool --args '{
+            "name": "code_exec_ruby",
+            "arguments": {
+                "code": "puts Array.new(100) { rand(1..100) }.join(\", \")",
+                "packages": [""]
+            }
+        }' | jq    """
     result = asyncio.run(run(method_name, args))
     print(json.dumps(result.model_dump(), indent=2))
 
diff --git a/src/code_execution.py b/src/code_execution.py
index 2d0a75b..1bb59b0 100644
--- a/src/code_execution.py
+++ b/src/code_execution.py
@@ -4,6 +4,8 @@
 import tempfile
 from typing import Annotated, Optional, List, Dict, Any
 from pydantic import Field
+# local:
+from src import config
 
 def run_command(cmd: List[str], env: Optional[Dict[str, str]] = None) -> Dict[str, Any]:
     """Executes a command using subprocess and returns output and errors."""
@@ -108,15 +110,7 @@ def code_exec_ruby(
     packages: Annotated[
         Optional[List[str]],
         Field(description="Optional list of gem names to install before execution.")
-    ] = None,
-    use_temp_dir: Annotated[
-        bool,
-        Field(description=(
-            "If True, code and dependencies are run in a temporary working directory. "
-            "Gems are installed in an isolated directory and will not affect or reuse the user's ~/.gem folder. "
-            "Not a secure sandbox."
-        ))
-    ] = False
+    ] = None
 ) -> Dict[str, Any]:
     """Executes a Ruby code snippet with optional gem dependencies.
 
@@ -132,7 +126,7 @@ def code_exec_ruby(
             - 'stdout': Captured standard output.
             - 'stderr': Captured standard error or install failure messages.
     """
-    if use_temp_dir:
+    if config.USE_TEMP_DIR:
         return run_in_tempdir(code, packages)
 
     # Otherwise, you can rely on pre-installed shared packages, if they exist:
diff --git a/src/config.py b/src/config.py
index 01b1341..31cbcec 100644
--- a/src/config.py
+++ b/src/config.py
@@ -17,6 +17,7 @@ def get_env_variable(var_name, required=True):
 PORT = int(os.environ.get('PORT', 8000))
 WEB_CONCURRENCY = int(os.environ.get('WEB_CONCURRENCY', 1))
 STDIO_MODE_ONLY = os.getenv("STDIO_MODE_ONLY", "false").lower() == "true"
+USE_TEMP_DIR = os.getenv("USE_TEMP_DIR", "false").lower() == "true"
 
 # Local or Not:
 is_one_off_dyno = os.getenv("DYNO") is not None