diff --git a/techrec/forge.py b/techrec/forge.py
index c636432..33efd89 100644
--- a/techrec/forge.py
+++ b/techrec/forge.py
@@ -8,7 +8,7 @@ from time import sleep
 from .config_manager import get_config
 
 
-def get_timefile_exact(time):
+def get_timefile_exact(time) -> str:
     """
     time is of type `datetime`; it is not "rounded" to match the real file;
     that work is done in get_timefile(time)
@@ -18,14 +18,14 @@ def get_timefile_exact(time):
     )
 
 
-def round_timefile(exact):
+def round_timefile(exact:datetime) -> datetime:
     """
     This will round the datetime, so to match the file organization structure
     """
     return datetime(exact.year, exact.month, exact.day, exact.hour)
 
 
-def get_timefile(exact):
+def get_timefile(exact:datetime) -> str:
     return get_timefile_exact(round_timefile(exact))
 
 
@@ -86,7 +86,7 @@ def mp3_join(named_intervals):
     return cmdline
 
 
-def create_mp3(start, end, outfile, options={}, **kwargs):
+def create_mp3(start: datetime, end: datetime, outfile: str, options={}, **kwargs):
     intervals = [
         (get_timefile(begin), start_cut, end_cut)
         for begin, start_cut, end_cut in get_files_and_intervals(start, end)