diff --git a/pytorch_lightning/tuner/auto_gpu_select.py b/pytorch_lightning/tuner/auto_gpu_select.py
index fd2ba4a1f3..3bd1ce52b5 100644
--- a/pytorch_lightning/tuner/auto_gpu_select.py
+++ b/pytorch_lightning/tuner/auto_gpu_select.py
@@ -17,6 +17,11 @@ from pytorch_lightning.utilities.exceptions import MisconfigurationException
 
 
 def pick_multiple_gpus(nb):
+    '''
+    Raises:
+        MisconfigurationException:
+            If ``gpus`` is set to 0, when ``auto_select_gpus=True``.
+    '''
     if nb == 0:
         raise MisconfigurationException(
             r"auto_select_gpus=True, gpus=0 is not a valid configuration.\
@@ -33,6 +38,11 @@ def pick_multiple_gpus(nb):
 
 
 def pick_single_gpu(exclude_gpus: list):
+    '''
+    Raises:
+        RuntimeError:
+            If you try to allocate a GPU, when no GPUs are available.
+    '''
     for i in range(torch.cuda.device_count()):
         if i in exclude_gpus:
             continue
diff --git a/pytorch_lightning/tuner/batch_size_scaling.py b/pytorch_lightning/tuner/batch_size_scaling.py
index c29cffc426..d6090a8e43 100644
--- a/pytorch_lightning/tuner/batch_size_scaling.py
+++ b/pytorch_lightning/tuner/batch_size_scaling.py
@@ -70,6 +70,13 @@ def scale_batch_size(
 
         **fit_kwargs: remaining arguments to be passed to .fit(), e.g., dataloader
             or datamodule.
+
+    Raises:
+        MisconfigurationException:
+            If field ``batch_arg_name`` is not found in ``model`` and ``model.hparams``, or
+            if batch scaling feature is used with dataloaders passed directly to ``.fit()``.
+        ValueError:
+            If mode in method ``scale_batch_size`` is neither ``power`` nor ``binsearch``.
     """
     if trainer.fast_dev_run:
         rank_zero_warn('Skipping batch size scaler since fast_dev_run is enabled.', UserWarning)
diff --git a/pytorch_lightning/tuner/lr_finder.py b/pytorch_lightning/tuner/lr_finder.py
index cf29799a05..1be9f5a616 100644
--- a/pytorch_lightning/tuner/lr_finder.py
+++ b/pytorch_lightning/tuner/lr_finder.py
@@ -106,6 +106,10 @@ def lr_find(
 
         update_attr: Whether to update the learning rate attribute or not.
 
+    Raises:
+        MisconfigurationException:
+            If learning rate/lr in ``model`` or ``model.hparams`` isn't overriden when ``auto_lr_find=True``, or
+            if you are using `more than one optimizer` with learning rate finder.
 
     Example::