diff --git a/tools-sync/scripts/sync_mcp_registrations.ps1 b/tools-sync/scripts/sync_mcp_registrations.ps1
index 7e9b4b5..e33ddde 100644
--- a/tools-sync/scripts/sync_mcp_registrations.ps1
+++ b/tools-sync/scripts/sync_mcp_registrations.ps1
@@ -18,6 +18,41 @@ $script:CodexBackupMade = $false
 $script:Failures = @()
 $CodexOnlyEnv = @("PYTHONIOENCODING", "PYTHONUTF8")
 
+function Test-TomllibPython([string]$Candidate) {
+    # tomllib needs CPython 3.11+; the Microsoft Store 'python' stub exits 49 and has no stdlib.
+    if (-not $Candidate) { return $false }
+    try { & $Candidate -c "import tomllib" 2>&1 | Out-Null } catch { return $false }
+    return ($LASTEXITCODE -eq 0)
+}
+
+function Resolve-PythonCommand([string]$Requested, [bool]$Explicit) {
+    # An explicit -PythonCommand is authoritative; only auto-probe the default.
+    if ($Explicit) { return $Requested }
+    if (Test-TomllibPython $Requested) { return $Requested }
+    $envFile = "$env:USERPROFILE\skills_env.md"
+    if (Test-Path -LiteralPath $envFile) {
+        $line = Select-String -LiteralPath $envFile -Pattern '^\s*CONDA_LANGGRAPH_PYTHON\s*=\s*(.+?)\s*$' |
+            Select-Object -First 1
+        if ($line) {
+            $cand = $line.Matches[0].Groups[1].Value.Trim()
+            if ((Test-Path -LiteralPath $cand) -and (Test-TomllibPython $cand)) {
+                Write-Host "python: falling back to CONDA_LANGGRAPH_PYTHON ($cand)"
+                return $cand
+            }
+        }
+    }
+    # Single-token candidates only: '& $cmd' treats the whole string as one exe name.
+    foreach ($cand in @("python3", "py")) {
+        if ((Get-Command $cand -ErrorAction SilentlyContinue) -and (Test-TomllibPython $cand)) {
+            Write-Host "python: falling back to '$cand'"
+            return $cand
+        }
+    }
+    throw "No tomllib-capable Python found ('$Requested' unusable). Pass -PythonCommand <path to CPython 3.11+>."
+}
+
+$PythonCommand = Resolve-PythonCommand $PythonCommand $PSBoundParameters.ContainsKey('PythonCommand')
+
 function ConvertTo-StringMap($Object) {
     $result = [ordered]@{}
     if ($null -eq $Object) { return $result }