diff --git a/docs/json.rst b/docs/json.rst
index 6e536e6b7..ef09cbf35 100644
--- a/docs/json.rst
+++ b/docs/json.rst
@@ -337,6 +337,12 @@ See ``delta_power_range_db`` for more explaination.
 |                                             |           | from `arXiv:1710.02225                      |
 |                                             |           | <https://arxiv.org/abs/1710.02225>`_).      |
 +---------------------------------------------+-----------+---------------------------------------------+
+| ``dispersion_tolerance``                    | (number)  | Optional. In ? Tuning parameter for ggn     |
+|                                             |           | model solution. Default value: 1            |
++---------------------------------------------+-----------+---------------------------------------------+
+| ``phase_shift_tolerance``                   | (number)  | Optional. In ? Tuning parameter for ggn     |
+|                                             |           | model solution. Defaut value: 0.1           |
++---------------------------------------------+-----------+---------------------------------------------+
 | ``nli_params.computed_channels``            | (list     | Optional. The exact channel indices         |
 |                                             | of        | (starting from 1) on which the NLI is       |
 |                                             | numbers)  | explicitly evaluated.                       |
diff --git a/gnpy/core/parameters.py b/gnpy/core/parameters.py
index 1689c644c..28bfc1089 100644
--- a/gnpy/core/parameters.py
+++ b/gnpy/core/parameters.py
@@ -61,6 +61,8 @@ def __init__(self, method='gn_model_analytic', dispersion_tolerance=1, phase_shi
         :params dispersion_tolerance: tuning parameter for ggn model solution
         :params phase_shift_tolerance: tuning parameter for ggn model solution
         :params computed_channels: the NLI is evaluated for these channels and extrapolated for the others
+        :params computed_number_of_channels: the NLI is evaluated for this nb of channels equally distributed
+        in the spectrum and extrapolated for the others
         """
         self.method = method.lower()
         self.dispersion_tolerance = dispersion_tolerance
@@ -72,7 +74,8 @@ def to_json(self):
         return {"method": self.method,
                 "dispersion_tolerance": self.dispersion_tolerance,
                 "phase_shift_tolerance": self.phase_shift_tolerance,
-                "computed_channels": self.computed_channels}
+                "computed_channels": self.computed_channels,
+                "computed_number_of_channels": self.computed_number_of_channels}
 
 
 class SimParams(Parameters):