diff --git a/mapytex/calculus/API/tokens/__init__.py b/mapytex/calculus/API/tokens/__init__.py
index 7163976..ea66dc5 100644
--- a/mapytex/calculus/API/tokens/__init__.py
+++ b/mapytex/calculus/API/tokens/__init__.py
@@ -10,52 +10,84 @@
 Tokens represents MathObject at API level
 
 """
-from ...core.MO import MO, MOnumber, MOstr
+from ...core.MO import MO, MOnumber, MOstr, moify
 from ...core.MO.fraction import MOFraction
 from ...core.MO.monomial import MOstrPower, MOMonomial
 from ...core.MO.polynomial import MOpolynomial
 from decimal import Decimal as _Decimal
+from .token import Token
 
 __all__ = ["factory"]
 
+def tokenify(mo, name="", ancestor=None):
+    """ Transform a MO or a python builtin to the appropriate token 
 
-def factory(exp, name="", ancestor=None):
-    """ Transform a Expression with on MathObject (from core) to a appropriate token (from API)
+    :param mo: the thing to turn into a Token
+    :param name: a virtual name of the toke
+    :param ancestor: its ancestor
 
     :example:
-    >>> from ..expression import Expression
-    >>> a = Expression(MOnumber(2))
-    >>> factory(a)
+    >>> a = MOnumber(2)
+    >>> tokenify(a)
     <Integer 2>
-    >>> a = Expression(MOnumber(2.5))
-    >>> factory(a)
-    <Decimal 2.5>
-    >>> a = Expression(MOFraction(2, 5))
-    >>> factory(a)
-    <Fraction 2 / 5>
-    >>> a = Expression(MOstr('x'))
-    >>> factory(a)
+    >>> tokenify(2)
+    <Integer 2>
+    >>> tokenify("x")
     <Linear x>
-    >>> a = Expression(MOstrPower('x', 2))
-    >>> factory(a)
+    >>> tokenify(_Decimal("2.2"))
+    <Decimal 2.2>
+    >>> tokenify("2.2")
+    <Decimal 2.2>
+    >>> tokenify(2.2)
+    <Decimal 2.20000000000000017763568394002504646778106689453125>
+
+    tokenify is idempotent on "mo" parameter
+
+    >>> a = MOnumber(2)
+    >>> ta = tokenify(a)
+    >>> ta == tokenify(ta)
+    True
+
+    """
+    if isinstance(mo, MO):
+        return _tokenify(mo, name, ancestor)
+    elif isinstance(mo, Token):
+        return _tokenify(mo._mo, name, ancestor)
+    return _tokenify(moify(mo), name, ancestor)
+
+
+def _tokenify(mo, name="", ancestor=None):
+    """ Transform a MO (from core) to the appropriate token (from API)
+
+    :example:
+    >>> a = MOnumber(2)
+    >>> _tokenify(a)
+    <Integer 2>
+    >>> a = MOnumber(2.5)
+    >>> _tokenify(a)
+    <Decimal 2.5>
+    >>> a = MOFraction(2, 5)
+    >>> _tokenify(a)
+    <Fraction 2 / 5>
+    >>> a = MOstr('x')
+    >>> _tokenify(a)
+    <Linear x>
+    >>> a = MOstrPower('x', 2)
+    >>> _tokenify(a)
     <Quadratic x^2>
-    >>> a = Expression(MOstrPower('x', 3))
-    >>> factory(a)
+    >>> a = MOstrPower('x', 3)
+    >>> _tokenify(a)
     <Polynomial x^3>
-    >>> a = Expression(MOMonomial(3, 'x', 1))
-    >>> factory(a)
+    >>> a = MOMonomial(3, 'x', 1)
+    >>> _tokenify(a)
     <Linear 3x>
-    >>> a = Expression(MOMonomial(3, 'x', 2))
-    >>> factory(a)
+    >>> a = MOMonomial(3, 'x', 2)
+    >>> _tokenify(a)
     <Quadratic 3x^2>
-    >>> a = Expression(MOMonomial(3, 'x', 3))
-    >>> factory(a)
+    >>> a = MOMonomial(3, 'x', 3)
+    >>> _tokenify(a)
     <Polynomial 3x^3>
     """
-    mo = exp._tree
-    if not isinstance(mo, MO):
-        raise TypeError(f"Can't build Token from not computed Expression (got {mo})")
-
     if isinstance(mo, MOnumber):
         if isinstance(mo.value, int):
             from .number import Integer
@@ -104,6 +136,47 @@ def factory(exp, name="", ancestor=None):
         raise TypeError(f"{type(mo)} is unknown MathObject")
 
 
+
+def factory(exp, name="", ancestor=None):
+    """ Transform a Expression with on single MathObject (from core) to a appropriate token (from API)
+
+    :example:
+    >>> from ..expression import Expression
+    >>> a = Expression(MOnumber(2))
+    >>> factory(a)
+    <Integer 2>
+    >>> a = Expression(MOnumber(2.5))
+    >>> factory(a)
+    <Decimal 2.5>
+    >>> a = Expression(MOFraction(2, 5))
+    >>> factory(a)
+    <Fraction 2 / 5>
+    >>> a = Expression(MOstr('x'))
+    >>> factory(a)
+    <Linear x>
+    >>> a = Expression(MOstrPower('x', 2))
+    >>> factory(a)
+    <Quadratic x^2>
+    >>> a = Expression(MOstrPower('x', 3))
+    >>> factory(a)
+    <Polynomial x^3>
+    >>> a = Expression(MOMonomial(3, 'x', 1))
+    >>> factory(a)
+    <Linear 3x>
+    >>> a = Expression(MOMonomial(3, 'x', 2))
+    >>> factory(a)
+    <Quadratic 3x^2>
+    >>> a = Expression(MOMonomial(3, 'x', 3))
+    >>> factory(a)
+    <Polynomial 3x^3>
+    """
+    mo = exp._tree
+    if not isinstance(mo, MO):
+        raise TypeError(f"Can't build Token from not computed Expression (got {mo})")
+
+    return _tokenify(mo, name, ancestor)
+
+
 # -----------------------------
 # Reglages pour 'vim'
 # vim:set autoindent expandtab tabstop=4 shiftwidth=4:
diff --git a/mapytex/calculus/core/MO/atoms.py b/mapytex/calculus/core/MO/atoms.py
index 6f5eba8..f9b505d 100644
--- a/mapytex/calculus/core/MO/atoms.py
+++ b/mapytex/calculus/core/MO/atoms.py
@@ -91,6 +91,12 @@ class MOnumber(Atom):
         >>> MOnumber(Decimal("-23.3"))
         <MOnumber - 23.3>
 
+        Or directly passe a decimal string
+        >>> MOnumber("23.3")
+        <MOnumber 23.3>
+        >>> MOnumber("-23.3")
+        <MOnumber - 23.3>
+
         MOnumber initialisation is idempotent
 
         >>> a = MOnumber(23)
@@ -100,7 +106,7 @@ class MOnumber(Atom):
         >>> MOnumber("a")
         Traceback (most recent call last):
             ...
-        mapytex.calculus.core.MO.exceptions.MOError: ('The value of an MOnumber need to be a int, a float or a Decimal', "(got <class 'str'>)")
+        mapytex.calculus.core.MO.exceptions.MOError: ('The value of an MOnumber need to be a int, a float, a Decimal or a decimal string', "(got <class 'str'>)")
 
         Atoms specific property and methods
 
@@ -122,10 +128,15 @@ class MOnumber(Atom):
         elif isinstance(value, float):
             Atom.__init__(self, Decimal(value))
         else:
-            raise MOError(
-                "The value of an MOnumber need to be a int, a float or a Decimal",
-                f"(got {type(value)})",
-            )
+            try:
+                float(value)
+            except (ValueError, TypeError):
+                raise MOError(
+                    "The value of an MOnumber need to be a int, a float, a Decimal or a decimal string",
+                    f"(got {type(value)})",
+                )
+            else:
+                Atom.__init__(self, Decimal(value))
 
         self._signature = "scalar"