diff --git a/src/scripts/mirror_export.py b/src/scripts/mirror_export.py
index d01e24b..5d44130 100644
--- a/src/scripts/mirror_export.py
+++ b/src/scripts/mirror_export.py
@@ -5,7 +5,7 @@ import sys, scriptengine as script_engine, os, traceback, time, codecs
 #
 #  - Structural nodes (Device, Application, Folder, ...) become directories.
 #  - Code-bearing nodes (Program, FB, Function, Method, Property, DUT, GVL,
-#    Interface, ...) become .iecst files in their parent directory.
+#    Interface, ...) become .st files in their parent directory.
 #  - If a code-bearing node has child code objects (e.g. an FB with methods)
 #    those children land in a sibling subdirectory with the parent's name.
 #  - Filesystem-illegal characters in CODESYS object names are replaced with
@@ -95,7 +95,7 @@ def write_one(parent_dir, name, decl, impl, project_path):
     if not os.path.exists(parent_dir):
         os.makedirs(parent_dir)
     kind = classify(decl)
-    fname = sanitise(name) + '.iecst'
+    fname = sanitise(name) + '.st'
     fpath = os.path.join(parent_dir, fname)
 
     lines = []
diff --git a/src/server.ts b/src/server.ts
index a3e3321..02371a7 100644
--- a/src/server.ts
+++ b/src/server.ts
@@ -1350,7 +1350,7 @@ export async function startMcpServer(config: ServerConfig): Promise<void> {
 
   s.tool(
     'mirror_export',
-    "Walks the CODESYS project tree and writes one .iecst file per code-bearing object into a filesystem mirror, preserving the project tree as nested directories. Programs / Function Blocks / Functions / Methods / Properties / DUTs / GVLs / Interfaces all become text files; structural nodes (Devices, Applications, Folders) become directories. Each file carries a header comment with its original CODESYS project path so a future write-back tool can map it back to set_pou_code's pouPath. Read-only -- does NOT modify the CODESYS project. UTF-8 output. If mirrorRoot is omitted, defaults to '<projectDir>/MCP/mirror'.",
+    "Walks the CODESYS project tree and writes one .st file per code-bearing object into a filesystem mirror, preserving the project tree as nested directories. Programs / Function Blocks / Functions / Methods / Properties / DUTs / GVLs / Interfaces all become text files; structural nodes (Devices, Applications, Folders) become directories. Each file carries a header comment with its original CODESYS project path so a future write-back tool can map it back to set_pou_code's pouPath. Read-only -- does NOT modify the CODESYS project. UTF-8 output. If mirrorRoot is omitted, defaults to '<projectDir>/MCP/mirror'.",
     {
       projectFilePath: z.string().describe("Path to the project file."),
       mirrorRoot: z.string().optional().describe("Filesystem path where the mirror tree gets written. If omitted, defaults to '<projectDir>/MCP/mirror'. Created automatically if missing; existing files at the same paths are overwritten."),