diff --git a/t3/main.py b/t3/main.py
index fd2a141f..757976e0 100755
--- a/t3/main.py
+++ b/t3/main.py
@@ -45,7 +45,12 @@
 from arc.species.species import ARCSpecies, check_label
 from arc.species.converter import check_xyz_dict
 
-from t3.common import PROJECTS_BASE_PATH, VALID_CHARS, delete_root_rmg_log, get_species_by_label, time_lapse
+from t3.common import (DATA_BASE_PATH,
+                       PROJECTS_BASE_PATH,
+                       VALID_CHARS,
+                       delete_root_rmg_log,
+                       get_species_by_label,
+                       time_lapse)
 from t3.logger import Logger
 from t3.runners.rmg_runner import rmg_runner
 from t3.schema import InputBase
@@ -177,6 +182,7 @@ def __init__(self,
         self.project_directory = self.schema['project_directory']
         self.t3 = self.schema['t3']
         self.rmg = self.schema['rmg']
+        self.rmg['database'] = auto_complete_rmg_libraries(database=self.rmg['database'])
         self.qm = self.schema['qm']
         self.verbose = self.schema['verbose']
 
@@ -1538,3 +1544,34 @@ def get_species_with_qm_label(species: Species,
                                 rmg_species=qm_species,
                                 )
     return qm_species
+
+
+def auto_complete_rmg_libraries(database: dict) -> dict:
+    """
+    Update the RMG libraries using auto-completion.
+
+    Args:
+        database (dict): The RMG libraries dictionary.
+
+    Returns:
+        dict: The updated RMG libraries dictionary.
+    """
+    database['thermo_libraries'] = database['thermo_libraries'] or list()
+    database['kinetics_libraries'] = database['kinetics_libraries'] or list()
+    if database['chemistry_sets'] is not None:
+        libraries_dict = read_yaml_file(path=os.path.join(DATA_BASE_PATH, 'libraries.yml'))
+        low_credence = database['use_low_credence_libraries']
+        for chemistry_set in database['chemistry_sets']:
+            if chemistry_set not in libraries_dict:
+                raise ValueError(f"Chemistry set '{chemistry_set}' not found in the libraries.yml file.")
+            for key, libraries in zip(['thermo', 'kinetics'], [database['thermo_libraries'], database['kinetics_libraries']]):
+                if key in libraries_dict[chemistry_set]:
+                    for entry in libraries_dict[chemistry_set][key]:
+                        if isinstance(entry, str) and entry not in libraries:
+                            libraries.append(entry)
+                        elif isinstance(entry, dict):
+                            if entry['credence'] == 'low' and low_credence or entry['credence'] != 'low' and entry['name'] not in libraries:
+                                libraries.append(entry['name'])
+    del database['chemistry_sets']
+    del database['use_low_credence_libraries']
+    return database