diff --git a/Readme.md b/Readme.md
index 82db1f5..b4facf0 100644
--- a/Readme.md
+++ b/Readme.md
@@ -275,9 +275,9 @@ res.should.be.json
 res.should.be.html
 ```
 
-## include(obj)
+## include(obj) or contain(obj)
 
-Assert that the given `obj` is present via `indexOf()`, so this works for strings, arrays, or custom objects implementing indexOf. Also it can assert if given object will have some sub-object
+Assert that the given `obj` is present via `indexOf()`, so this works for strings, arrays, or custom objects implementing indexOf. Also it can assert if given object will have some sub-object.
 
 Assert array value:
 ```javascript
diff --git a/lib/should.js b/lib/should.js
index 714a92f..9e1c732 100644
--- a/lib/should.js
+++ b/lib/should.js
@@ -41,7 +41,7 @@ util.merge(should, assert);
 /**
  * Assert _obj_ exists, with optional message.
  *
- * @param {Mixed} obj
+ * @param {*} obj
  * @param {String} [msg]
  * @api public
  */
@@ -57,7 +57,7 @@ should.exist = should.exists = function(obj, msg) {
 /**
  * Asserts _obj_ does not exist, with optional message.
  *
- * @param {Mixed} obj
+ * @param {*} obj
  * @param {String} [msg]
  * @api public
  */
@@ -95,7 +95,7 @@ Object.defineProperty(Object.prototype, 'should', {
 /**
  * Initialize a new `Assertion` with the given _obj_.
  *
- * @param {Mixed} obj
+ * @param {*} obj
  * @api private
  */
 
@@ -115,15 +115,18 @@ Assertion.prototype = {
    * Assert _expr_ with the given _msg_ and _negatedMsg_.
    *
    * @param {Boolean} expr
-   * @param {String} msg
-   * @param {String} negatedMsg
-   * @param {Object} expected
+   * @param {function} msg
+   * @param {function} negatedMsg
+   * @param {Object} [expected]
+   * @param {Boolean} [showDiff]
+   * @param {String} [description]
    * @api private
    */
 
-  assert: function(expr, msg, negatedMsg, expected, showDiff){
-    var msg = this.negate ? negatedMsg : msg
-      , ok = this.negate ? !expr : expr
+  assert: function(expr, msg, negatedMsg, expected, showDiff, description){
+    msg = this.negate ? negatedMsg : msg
+
+    var ok = this.negate ? !expr : expr
       , obj = this.obj;
 
     if (ok) return;
@@ -137,6 +140,7 @@ Assertion.prototype = {
     });
 
     err.showDiff = showDiff;
+    err.description = description
 
     throw err;
   },
@@ -342,35 +346,38 @@ Assertion.prototype = {
   /**
    * Assert equal.
    *
-   * @param {Mixed} val
+   * @param {*} val
    * @param {String} description
    * @api public
    */
 
-  eql: function(val, desc){
+  eql: function(val, description){
     this.assert(
         eql(val, this.obj)
-      , function(){ return 'expected ' + this.inspect + ' to equal ' + should.inspect(val) + (desc ? " | " + desc : "") }
-      , function(){ return 'expected ' + this.inspect + ' to not equal ' + should.inspect(val) + (desc ? " | " + desc : "") }
+      , function(){ return 'expected ' + this.inspect + ' to equal ' + should.inspect(val) + (description ? " | " + description : "") }
+      , function(){ return 'expected ' + this.inspect + ' to not equal ' + should.inspect(val) + (description ? " | " + description : "") }
       , val
-      , true);
+      , true
+      , description);
     return this;
   },
 
   /**
    * Assert strict equal.
    *
-   * @param {Mixed} val
+   * @param {*} val
    * @param {String} description
    * @api public
    */
 
-  equal: function(val, desc){
+  equal: function(val, description){
     this.assert(
         val === this.obj
-      , function(){ return 'expected ' + this.inspect + ' to equal ' + should.inspect(val) + (desc ? " | " + desc : "") }
-      , function(){ return 'expected ' + this.inspect + ' to not equal ' + should.inspect(val) + (desc ? " | " + desc : "") }
-      , val);
+      , function(){ return 'expected ' + this.inspect + ' to equal ' + should.inspect(val) + (description ? " | " + description : "") }
+      , function(){ return 'expected ' + this.inspect + ' to not equal ' + should.inspect(val) + (description ? " | " + description : "") }
+      , val
+      , void 0
+      , description);
     return this;
   },
 
@@ -383,12 +390,15 @@ Assertion.prototype = {
    * @api public
    */
 
-  within: function(start, finish, desc){
+  within: function(start, finish, description){
     var range = start + '..' + finish;
     this.assert(
         this.obj >= start && this.obj <= finish
-      , function(){ return 'expected ' + this.inspect + ' to be within ' + range + (desc ? " | " + desc : "") }
-      , function(){ return 'expected ' + this.inspect + ' to not be within ' + range + (desc ? " | " + desc : "") });
+      , function(){ return 'expected ' + this.inspect + ' to be within ' + range + (description ? " | " + description : "") }
+      , function(){ return 'expected ' + this.inspect + ' to not be within ' + range + (description ? " | " + description : "") }
+      , void 0
+      , void 0
+      , description);
     return this;
   },
 
@@ -405,23 +415,28 @@ Assertion.prototype = {
     this.assert(
       Math.abs(this.obj - value) <= delta
       , function(){ return 'expected ' + this.inspect + ' to be approximately ' + value + " +- " + delta + (description ? " | " + description : "") }
-      , function(){ return 'expected ' + this.inspect + ' to not be approximately ' + value + " +- " + delta + (description ? " | " + description : "") });
+      , function(){ return 'expected ' + this.inspect + ' to not be approximately ' + value + " +- " + delta + (description ? " | " + description : "") }
+      , void 0
+      , void 0
+      , description);
     return this;
   },
 
   /**
    * Assert typeof.
    *
-   * @param {Mixed} type
+   * @param {*} type
    * @param {String} description
    * @api public
    */
-
-  type: function(type, desc){
+  type: function(type, description){
     this.assert(
         type == typeof this.obj
-      , function(){ return 'expected ' + this.inspect + ' to have type ' + type + (desc ? " | " + desc : "") }
-      , function(){ return 'expected ' + this.inspect + ' not to have type ' + type  + (desc ? " | " + desc : "") })
+      , function(){ return 'expected ' + this.inspect + ' to have type ' + type + (description ? " | " + description : "") }
+      , function(){ return 'expected ' + this.inspect + ' not to have type ' + type  + (description ? " | " + description : "") }
+      , void 0
+      , void 0
+      , description);
     return this;
   },
 
@@ -433,12 +448,15 @@ Assertion.prototype = {
    * @api public
    */
 
-  instanceof: function(constructor, desc){
+  instanceof: function(constructor, description){
     var name = constructor.name;
     this.assert(
         this.obj instanceof constructor
-      , function(){ return 'expected ' + this.inspect + ' to be an instance of ' + name + (desc ? " | " + desc : "") }
-      , function(){ return 'expected ' + this.inspect + ' not to be an instance of ' + name + (desc ? " | " + desc : "") });
+      , function(){ return 'expected ' + this.inspect + ' to be an instance of ' + name + (description ? " | " + description : "") }
+      , function(){ return 'expected ' + this.inspect + ' not to be an instance of ' + name + (description ? " | " + description : "") }
+      , void 0
+      , void 0
+      , description);
     return this;
   },
 
@@ -526,11 +544,14 @@ Assertion.prototype = {
    * @api public
    */
 
-  above: function(n, desc){
+  above: function(n, description){
     this.assert(
         this.obj > n
-      , function(){ return 'expected ' + this.inspect + ' to be above ' + n + (desc ? " | " + desc : "") }
-      , function(){ return 'expected ' + this.inspect + ' to be below ' + n + (desc ? " | " + desc : "") });
+      , function(){ return 'expected ' + this.inspect + ' to be above ' + n + (description ? " | " + description : "") }
+      , function(){ return 'expected ' + this.inspect + ' to be below ' + n + (description ? " | " + description : "") }
+      , void 0
+      , void 0
+      , description);
     return this;
   },
 
@@ -542,11 +563,14 @@ Assertion.prototype = {
    * @api public
    */
 
-  below: function(n, desc){
+  below: function(n, description){
     this.assert(
         this.obj < n
-      , function(){ return 'expected ' + this.inspect + ' to be below ' + n + (desc ? " | " + desc : "") }
-      , function(){ return 'expected ' + this.inspect + ' to be above ' + n + (desc ? " | " + desc : "") });
+      , function(){ return 'expected ' + this.inspect + ' to be below ' + n + (description ? " | " + description : "") }
+      , function(){ return 'expected ' + this.inspect + ' to be above ' + n + (description ? " | " + description : "") }
+      , void 0
+      , void 0
+      , description);
     return this;
   },
 
@@ -558,11 +582,14 @@ Assertion.prototype = {
    * @api public
    */
 
-  match: function(regexp, desc){
+  match: function(regexp, description){
     this.assert(
         regexp.exec(this.obj)
-      , function(){ return 'expected ' + this.inspect + ' to match ' + regexp + (desc ? " | " + desc : "") }
-      , function(){ return 'expected ' + this.inspect + ' not to match ' + regexp + (desc ? " | " + desc : "") });
+      , function(){ return 'expected ' + this.inspect + ' to match ' + regexp + (description ? " | " + description : "") }
+      , function(){ return 'expected ' + this.inspect + ' not to match ' + regexp + (description ? " | " + description : "") }
+      , void 0
+      , void 0
+      , description);
     return this;
   },
 
@@ -574,13 +601,16 @@ Assertion.prototype = {
    * @api public
    */
 
-  length: function(n, desc){
+  length: function(n, description){
     this.obj.should.have.property('length');
     var len = this.obj.length;
     this.assert(
         n == len
-      , function(){ return 'expected ' + this.inspect + ' to have a length of ' + n + ' but got ' + len + (desc ? " | " + desc : "") }
-      , function(){ return 'expected ' + this.inspect + ' to not have a length of ' + len + (desc ? " | " + desc : "") });
+      , function(){ return 'expected ' + this.inspect + ' to have a length of ' + n + ' but got ' + len + (description ? " | " + description : "") }
+      , function(){ return 'expected ' + this.inspect + ' to not have a length of ' + len + (description ? " | " + description : "") }
+      , void 0
+      , void 0
+      , description);
     return this;
   },
 
@@ -588,29 +618,35 @@ Assertion.prototype = {
    * Assert property _name_ exists, with optional _val_.
    *
    * @param {String} name
-   * @param {Mixed} [val]
+   * @param {*} [val]
    * @param {String} description
    * @api public
    */
 
-  property: function(name, val, desc){
+  property: function(name, val, description){
     if (this.negate && undefined !== val) {
       if (undefined === this.obj[name]) {
-        throw new Error(this.inspect + ' has no property ' + should.inspect(name) + (desc ? " | " + desc : ""));
+        throw new Error(this.inspect + ' has no property ' + should.inspect(name) + (description ? " | " + description : ""));
       }
     } else {
       this.assert(
           undefined !== this.obj[name]
-        , function(){ return 'expected ' + this.inspect + ' to have a property ' + should.inspect(name) + (desc ? " | " + desc : "") }
-        , function(){ return 'expected ' + this.inspect + ' to not have a property ' + should.inspect(name) + (desc ? " | " + desc : "") });
+        , function(){ return 'expected ' + this.inspect + ' to have a property ' + should.inspect(name) + (description ? " | " + description : "") }
+        , function(){ return 'expected ' + this.inspect + ' to not have a property ' + should.inspect(name) + (description ? " | " + description : "") }
+        , void 0
+        , void 0
+        , description);
     }
 
     if (undefined !== val) {
       this.assert(
           val === this.obj[name]
         , function(){ return 'expected ' + this.inspect + ' to have a property ' + should.inspect(name)
-          + ' of ' + should.inspect(val) + ', but got ' + should.inspect(this.obj[name]) + (desc ? " | " + desc : "") }
-        , function(){ return 'expected ' + this.inspect + ' to not have a property ' + should.inspect(name) + ' of ' + should.inspect(val) + (desc ? " | " + desc : "") });
+          + ' of ' + should.inspect(val) + ', but got ' + should.inspect(this.obj[name]) + (description ? " | " + description : "") }
+        , function(){ return 'expected ' + this.inspect + ' to not have a property ' + should.inspect(name) + ' of ' + should.inspect(val) + (description ? " | " + description : "") }
+        , void 0
+        , void 0
+        , description);
     }
 
     this.obj = this.obj[name];
@@ -668,11 +704,14 @@ Assertion.prototype = {
    * @api public
    */
 
-  ownProperty: function(name, desc){
+  ownProperty: function(name, description){
     this.assert(
       hasOwnProperty.call(this.obj, name)
-      , function(){ return 'expected ' + this.inspect + ' to have own property ' + should.inspect(name) + (desc ? " | " + desc : "") }
-      , function(){ return 'expected ' + this.inspect + ' to not have own property ' + should.inspect(name) + (desc ? " | " + desc : "") });
+      , function(){ return 'expected ' + this.inspect + ' to have own property ' + should.inspect(name) + (description ? " | " + description : "") }
+      , function(){ return 'expected ' + this.inspect + ' to not have own property ' + should.inspect(name) + (description ? " | " + description : "") }
+      , void 0
+      , void 0
+      , description);
     this.obj = this.obj[name];
     return this;
   },
@@ -680,52 +719,64 @@ Assertion.prototype = {
   /**
    * Assert that string starts with `str`.
    * @param {String} str
-   * @param {String} desc
+   * @param {String} description
    * @api public
    */
 
-  startWith: function(str, desc) {
+  startWith: function(str, description) {
     this.assert(0 === this.obj.indexOf(str)
-    , function() { return 'expected ' + this.inspect + ' to start with ' + should.inspect(str) + (desc ? " | " + desc : "") }
-    , function() { return 'expected ' + this.inspect + ' to not start with ' + should.inspect(str) + (desc ? " | " + desc : "") });
+    , function() { return 'expected ' + this.inspect + ' to start with ' + should.inspect(str) + (description ? " | " + description : "") }
+    , function() { return 'expected ' + this.inspect + ' to not start with ' + should.inspect(str) + (description ? " | " + description : "") }
+    , void 0
+    , void 0
+    , description);
     return this;
   },
 
   /**
    * Assert that string ends with `str`.
    * @param {String} str
-   * @param {String} desc
+   * @param {String} description
    * @api public
    */
 
-  endWith: function(str, desc) {
+  endWith: function(str, description) {
     this.assert(-1 !== this.obj.indexOf(str, this.obj.length - str.length)
-    , function() { return 'expected ' + this.inspect + ' to end with ' + should.inspect(str) + (desc ? " | " + desc : "") }
-    , function() { return 'expected ' + this.inspect + ' to not end with ' + should.inspect(str) + (desc ? " | " + desc : "") });
+    , function() { return 'expected ' + this.inspect + ' to end with ' + should.inspect(str) + (description ? " | " + description : "") }
+    , function() { return 'expected ' + this.inspect + ' to not end with ' + should.inspect(str) + (description ? " | " + description : "") }
+    , void 0
+    , void 0
+    , description);
     return this;
   },
 
   /**
    * Assert that `obj` is present via `.indexOf()` or that `obj` contains some sub-object.
    *
-   * @param {Mixed} obj
+   * @param {*} obj
    * @param {String} description
    * @api public
    */
 
-  include: function(obj, desc){
+  include: function(obj, description){
     if (obj.constructor == Object){
       var cmp = {};
       for (var key in obj) cmp[key] = this.obj[key];
       this.assert(
           eql(cmp, obj)
-        , function(){ return 'expected ' + this.inspect + ' to include an object equal to ' + should.inspect(obj) + (desc ? " | " + desc : "") }
-        , function(){ return 'expected ' + this.inspect + ' to not include an object equal to ' + should.inspect(obj) + (desc ? " | " + desc : "") });
+        , function(){ return 'expected ' + this.inspect + ' to include an object equal to ' + should.inspect(obj) + (description ? " | " + description : "") }
+        , function(){ return 'expected ' + this.inspect + ' to not include an object equal to ' + should.inspect(obj) + (description ? " | " + description : "") }
+        , void 0
+        , void 0
+        , description);
     } else {
       this.assert(
           ~this.obj.indexOf(obj)
-        , function(){ return 'expected ' + this.inspect + ' to include ' + should.inspect(obj) + (desc ? " | " + desc : "") }
-        , function(){ return 'expected ' + this.inspect + ' to not include ' + should.inspect(obj) + (desc ? " | " + desc : "") });
+        , function(){ return 'expected ' + this.inspect + ' to include ' + should.inspect(obj) + (description ? " | " + description : "") }
+        , function(){ return 'expected ' + this.inspect + ' to not include ' + should.inspect(obj) + (description ? " | " + description : "") }
+        , void 0
+        , void 0
+        , description);
     }
     return this;
   },
@@ -738,15 +789,17 @@ Assertion.prototype = {
    * @api public
    */
 
-  includeEql: function(obj, desc){
+  includeEql: function(obj, description){
     this.assert(
       this.obj.some(function(item) { return eql(obj, item); })
-      , function(){ return 'expected ' + this.inspect + ' to include an object equal to ' + should.inspect(obj) + (desc ? " | " + desc : "") }
-      , function(){ return 'expected ' + this.inspect + ' to not include an object equal to ' + should.inspect(obj) + (desc ? " | " + desc : "") });
+      , function(){ return 'expected ' + this.inspect + ' to include an object equal to ' + should.inspect(obj) + (description ? " | " + description : "") }
+      , function(){ return 'expected ' + this.inspect + ' to not include an object equal to ' + should.inspect(obj) + (description ? " | " + description : "") }
+      , void 0
+      , void 0
+      , description);
     return this;
   },
 
-
   /**
    * Assert exact keys or inclusion of keys by using
    * the `.include` modifier.