diff --git a/nuwavsource/nuwavsource.py b/nuwavsource/nuwavsource.py
index c41e9ca..ab22a88 100644
--- a/nuwavsource/nuwavsource.py
+++ b/nuwavsource/nuwavsource.py
@@ -17,7 +17,10 @@ from warnings import filterwarnings
 filterwarnings('ignore')
 
 
-def get_link_list(folder, sort_list=True):
+def get_link_list(folder: str, sort_list=True) -> list[str]:
+    """
+    Returns array of paths to all *_cl.evt files in the directory recursively. 
+    """
     links = glob(f'{folder}\\**\\*_cl.evt', recursive=True)
     if sort_list:
         sorted_list = sorted(links, key=lambda x: stat(x).st_size)
@@ -26,7 +29,10 @@ def get_link_list(folder, sort_list=True):
         return np.array(links)
 
 
-def binary_array(num):
+def binary_array(num: int) -> list[list[bool]]:
+    """
+    Returns list of all possible combinations of num of bool values.
+    """
     variants = [[0, 1], ]*num
     out = np.zeros((2**num, num), bool)
     for idx, level in enumerate(itertools.product(*variants)):
@@ -34,8 +40,12 @@ def binary_array(num):
     return out
 
 
-def create_array(filename, mode='Sky'):
-    temp = fits.getdata(filename, 1)
+def create_array(file_path: str, mode='Sky') -> list[int]:
+    """
+    Returns a 2d array of counts for given observation file.
+    Modes 'Sky' and 'Det' return arrays in (X,Y) and DET1 respectively.
+    """
+    temp = fits.getdata(file_path, 1)
     if mode == 'Sky':
         return np.histogram2d(temp['Y'],
                               temp['X'],
@@ -49,6 +59,10 @@ def create_array(filename, mode='Sky'):
 
 
 def get_wcs(file):
+    """
+    Returns WCS for given observation.
+    Note that argument here is an opened fits file, not a path.
+    """
     header = file[1].header
     wcs = WCS({
         'CTYPE1': header['TCTYP38'], 'CTYPE2': header['TCTYP39'],
@@ -61,7 +75,10 @@ def get_wcs(file):
     return wcs
 
 
-def atrous(level=0, max_size=1001):
+def atrous(level=0, max_size=1001) -> list[list[float]]:
+    """
+    Returns a trou kernel with the size 2**level and corresponding shape.
+    """
     base = 1/256*np.array([
         [1,  4,  6,  4, 1],
         [4, 16, 24, 16, 4],
@@ -78,7 +95,10 @@ def atrous(level=0, max_size=1001):
     return output
 
 
-def gauss(level=0, max_size=1000):
+def gauss(level=0, max_size=1000) -> list[list[float]]:
+    """
+    Returns gaussian kernel with sigma = 2**level
+    """
     size = min(5*2**(level+1)+1, max_size)
     sigma = 2**(level)
     A = 1/(2*np.pi*sigma**2)**0.5
@@ -88,6 +108,9 @@ def gauss(level=0, max_size=1000):
 
 
 def adjecent(array):
+    """
+    Returns two lists of indices of cells adjecent or diagonal to non-zero cells of given array
+    """
     grid = np.array([
         [1, 1, 1],
         [1, 0, 1],
@@ -104,6 +127,9 @@ def adjecent(array):
 
 
 def add_borders(array, middle=True):
+    """
+    Returns border mask for an DET1 observation array
+    """
     mask = np.zeros(array.shape)
     datax, datay = np.any(array > 0, 0), np.any(array > 0, 1)
     # Add border masks
@@ -119,6 +145,9 @@ def add_borders(array, middle=True):
 
 
 def fill_poisson(array, size_input=32):
+    """
+    Fills all masked elements of an array with poisson signal with local expected value.
+    """
     if not (isinstance(array, np.ma.MaskedArray)):
         print('No mask found')
         return array
@@ -137,6 +166,10 @@ def fill_poisson(array, size_input=32):
 
 
 def mirror(array):
+    """
+    Returns 3 times bigger array with mirrored elements.
+    Original array is located in center.
+    """
     size = array.shape[0]
     output = np.tile(array, (3, 3))
     output[0:size] = np.flipud(output[0:size])
@@ -147,7 +180,10 @@ def mirror(array):
 
 
 class Observation:
-    def __init__(self, file_name, E_borders=[3,20]):
+    """
+    Main class, contains information about the observation given.
+    """
+    def __init__(self, file_name, E_borders=[3, 20]):
         self.filename = file_name
         self.name = file_name[file_name.find('nu'):].replace('_cl.evt','')
         with fits.open(file_name) as file:
@@ -163,11 +199,19 @@ class Observation:
         self.exposure = self.header['EXPOSURE']
 
     def get_coeff(self):
+        """
+        Returns normalalizing coefficients for different chips of the observation detector.
+        Coefficients are obtained from stacked observations in OCC mode.
+        """
         coeff = np.array([0.977, 0.861, 1.163, 1.05]) if self.det == 'A' else np.array([1.004, 0.997, 1.025, 0.979])
         resized_coeff = (coeff).reshape(2, 2).repeat(180, 0).repeat(180, 1)
         return resized_coeff
 
     def get_data(self, file, E_borders=[3, 20]):
+        """
+        Returns masked array with DET1 image data for given energy band.
+        Mask is created from observations badpix tables and to mask the border and gaps. 
+        """
         PI_min, PI_max = (np.array(E_borders)-1.6)/0.04
         data = file[1].data.copy()
         idx_mask = (data['STATUS'].sum(1) == 0)        
@@ -182,6 +226,9 @@ class Observation:
         return output, mask
 
     def get_bad_pix(self, file):
+        """
+        Creates a mask for observation based on badpix tables.
+        """
         output = np.zeros((360, 360))
         kernel = np.ones((5, 5))
         for i in range(4):
@@ -197,6 +244,9 @@ class Observation:
         return output
 
     def wavdecomp(self, mode='gauss', thresh=False, occ_coeff=False):
+        """
+        Performs a wavelet decomposition of image.
+        """
         # THRESHOLD
         if type(thresh) is int:
             thresh_max, thresh_add = thresh, thresh/2
@@ -245,6 +295,9 @@ class Observation:
         return conv_out
 
     def region_to_raw(self, region):
+        """
+        Returns a hdu_list with positions of masked pixels in RAW coordinates.
+        """
         x_region, y_region = np.where(region)
         tables = []
         for i in range(4):
@@ -349,6 +402,10 @@ def process(args):
 
 
 def process_folder(input_folder=None, start_new_file=None, fits_folder=None, thresh=None):
+    """
+    Generates a fits-table of parameters, folder with mask images in DET1 and BADPIX tables in RAW for all observations in given folder.
+    Note that observations with exposure < 1000 sec a skipped.
+    """
     # DIALOGUE
     if not (input_folder):
         print('Enter path to the input folder')