diff --git a/tools/build_translations.py b/tools/build_translations.py
index 91c4e9509..a16f7152d 100644
--- a/tools/build_translations.py
+++ b/tools/build_translations.py
@@ -150,7 +150,8 @@ limiter = RateLimiter(LIMIT_RPM, LIMIT_TPM)
 # Prompts
 # ---------------------------------------------------------------------------
 AGENT_NEW_FILE_PROMPT = """\
-You are an autonomous documentation translator.
+You are an autonomous documentation translator. You are translating the FTXUI
+C++ library from English into {lang_name} ("{lang_code}").
 
 GOAL
 - Translate a single, NEW file to {lang_name} ("{lang_code}").
@@ -173,7 +174,8 @@ TOOLS: {allowed_tools}.
 """
 
 AGENT_DIFF_FILE_PROMPT = """\
-You are an autonomous documentation translator.
+You are an autonomous documentation translator. You are translating the FTXUI
+C++ library from English into {lang_name} ("{lang_code}").
 
 GOAL
 - Update existing translation: {tx_root}/{rel_path}
@@ -195,6 +197,16 @@ WORKFLOW
 4. ONLY update text where the source changed.
 5. DO NOT translate code.
 
+RULES:
+1. Translate ONLY documentation:
+   * C++ comments (//, /* ... */)
+   * Doxygen comments (///, /** ... */).
+   * Prose in Markdown.
+2. DO NOT translate/modify:
+   * C/C++ code, identifiers, includes, macros.
+   * Doxygen commands/params.
+   * Markdown code fences/URLs.
+
 TOOLS: {allowed_tools}.
 """
 
@@ -404,8 +416,14 @@ def main() -> None:
     all_files.sort()
 
     for lang_code in args.langs:
-        lang_name = LANG_NAMES.get(lang_code, lang_code)
+        lang_name = LANG_NAMES.get(lang_code, "")
         print_step(f"Processing Language: {lang_name} ({lang_code})")
+
+        if not lang_name:
+            exit_msg = f"Unknown language code: {lang_code}. Please update LANG_NAMES dictionary."
+            print_err(exit_msg)
+            sys.exit(1)
+
         
         checkout_or_create_branch(tx_dir, lang_code)