diff --git a/umu/umu_run.py b/umu/umu_run.py
index ec8feb3d..859ca02f 100755
--- a/umu/umu_run.py
+++ b/umu/umu_run.py
@@ -23,7 +23,7 @@
 from re import match
 from socket import AF_INET, SOCK_DGRAM, socket
 from subprocess import Popen
-from typing import Any
+from typing import Any, Optional
 
 from filelock import FileLock
 from urllib3 import PoolManager, Retry
@@ -136,7 +136,7 @@ def check_env(
     env["WINEPREFIX"] = os.environ.get("WINEPREFIX", "")
 
     # Skip Proton if running a native Linux executable
-    if os.environ.get("UMU_NO_PROTON") == "1" or os.environ.get("UMU_NO_TOOL") == "1":
+    if os.environ.get("UMU_NO_PROTON") == "1":
         return env
 
     # Proton Version
@@ -269,7 +269,6 @@ def set_env(
     env["UMU_NO_RUNTIME"] = os.environ.get("UMU_NO_RUNTIME") or ""
     env["UMU_RUNTIME_UPDATE"] = os.environ.get("UMU_RUNTIME_UPDATE") or ""
     env["UMU_NO_PROTON"] = os.environ.get("UMU_NO_PROTON") or ""
-    env["UMU_NO_TOOL"] = os.environ.get("UMU_NO_TOOL") or ""
 
     # Proton logging (to stdout)
     # Check for PROTON_LOG because it redirects output to log file
@@ -315,7 +314,7 @@ def enable_steam_game_drive(env: dict[str, str]) -> dict[str, str]:
 def build_command(
     env: dict[str, str],
     local: Path,
-    opts: list[str] = None,
+    opts: Optional | list[str] = None,
 ) -> tuple[Path | str, ...]:
     """Build the command to be executed."""
     shim: Path = local.joinpath("umu-shim")
@@ -337,20 +336,34 @@ def build_command(
     # Will run the game within the Steam Runtime w/o Proton
     # Ideally, for reliability, executables should be compiled within
     # the Steam Runtime
-    if env.get("UMU_NO_TOOL") == "1" or env.get("UMU_NO_PROTON") == "1":
-        log.debug("Compatibility tool disabled. Executing linux-native executable %s", env["EXE"])
+    if env.get("UMU_NO_PROTON") == "1":
+        log.debug(
+            "Compatibility tool disabled. Executing linux-native executable %s", env["EXE"]
+        )
         return (
             *runtime.command(env["PROTON_VERB"]),
             env["EXE"],
             *opts,
         )
 
-    compat_tool = CompatibilityTool(env["PROTONPATH"], shim, runtime)
+    # Setup compatibility tool
+    # If the user explicitly requested to run without the runtime,
+    # force runtime to None
+    compat_tool = CompatibilityTool(
+        env["PROTONPATH"],
+        shim,
+        None if env["UMU_NO_RUNTIME"] == "1" else runtime
+    )
     log.info("Using compatibility tool %s", compat_tool.display_name)
-    env["UMU_NO_RUNTIME"] = "1" if compat_tool.runtime is None else "0"
+    # Will run the game outside the Steam Runtime w/ Proton
+    if not compat_tool.runtime_enabled:
+        log.warning("Runtime Platform disabled")
 
     # Winetricks
-    if env.get("EXE", "").endswith("winetricks") and opts and compat_tool.layer == "proton":
+    if env.get("EXE", "").endswith("winetricks") and opts:
+        if compat_tool.layer != "proton":
+            err: str = "Winetricks is available only on Proton and Proton-derived tools"
+            raise ValueError(err)
         # The position of arguments matter for winetricks
         # Usage: ./winetricks [options] [command|verb|path-to-verb] ...
         return (
@@ -360,10 +373,6 @@ def build_command(
             *opts,
         )
 
-    # Will run the game outside the Steam Runtime w/ Proton
-    if env.get("UMU_NO_RUNTIME") == "1":
-        log.warning("Runtime Platform disabled")
-
     return (
         *compat_tool.command(env["PROTON_VERB"]),
         env["EXE"],
@@ -763,7 +772,6 @@ def umu_run(args: Namespace | tuple[str, list[str]]) -> int:
         "UMU_NO_RUNTIME": "",
         "UMU_RUNTIME_UPDATE": "",
         "UMU_NO_PROTON": "",
-        "UMU_NO_TOOL": "",
     }
     opts: list[str] = []
     prereq: bool = False
diff --git a/umu/umu_util.py b/umu/umu_util.py
index 956fb25e..81cd9c11 100644
--- a/umu/umu_util.py
+++ b/umu/umu_util.py
@@ -320,10 +320,10 @@ def required_tool_appid(self) ->  str:  # noqa: D102
         return self.tool_manifest.get("require_tool_appid", None)
 
     @property
-    def required_tool_name(self) -> None:
+    def required_tool_name(self) -> tuple:
         """Map the required tool's appid to a tuple of commonly used names."""
         if self.required_tool_appid is None:
-            return None
+            return None, None
         return RUNTIME_VERSIONS[self.required_tool_appid]
 
     @property
@@ -352,7 +352,7 @@ def __init__(self, path: str) -> None:  # noqa: D107
 class CompatibilityTool(SteamBase):
     """A compatibility tool (Proton, luxtorpeda, etc)."""
 
-    def __init__(self, tool_path: str, shim: Path, runtime: SteamRuntime) -> None:  # noqa: D107
+    def __init__(self, tool_path: str, shim: Path, runtime: None | SteamRuntime) -> None:  # noqa: D107
         super().__init__(tool_path)
         self.shim = shim
         self.runtime = runtime if self.required_tool_appid is not None else None
@@ -366,10 +366,15 @@ def __init__(self, tool_path: str, shim: Path, runtime: SteamRuntime) -> None:
     def display_name(self) -> str:  # noqa: D102
         return self.compatibility_tool["display_name"]
 
+    @property
+    def runtime_enabled(self) -> bool:
+        """Report if the compatibility tool has a configured runtime."""
+        return self.runtime is not None
+
     def command(self, verb: str) -> list[str]:
         """Return the fully qualified command for the tool .
 
-        If the tool uses a runtime, it's entry point is prepended to the tool's command.
+        If the tool uses a runtime, its entry point is prepended to the tool's command.
         """
         cmd = self.runtime.command(verb) if self.runtime is not None else []
         cmd.append(self.shim.as_posix())