diff --git a/README.md b/README.md
index 235468d..b713a58 100644
--- a/README.md
+++ b/README.md
@@ -65,15 +65,6 @@ docuri.parts({ type: 'mytype', subtype: 'mysubtype' });
 // ['mytype', undefined, 'mysubtype']
 ```
 
-### `arity(objectOrString)`
-Length of parts:
-```js
-docuri.arity('mytype/myid/');
-// 2 
-docuri.arity({ type: 'mytype', subtype: 'mysubtype' });
-// 3
-```
-
 ### `docuri.definition([array])`
 Access or use custom definition:
 ```js
diff --git a/index.js b/index.js
index b808a1d..7ca8d9f 100644
--- a/index.js
+++ b/index.js
@@ -72,14 +72,3 @@ docuri.merge = function(obj, objToMerge) {
   return docuri.stringify(obj);
 };
 
-docuri.arity = function(obj) {
-  if (typeof obj === 'string') {
-    obj = docuri.parse(obj);
-  }
-
-  return docuri.parts(obj).length;
-};
-
-
-module.exports = docuri;
-
diff --git a/package.json b/package.json
index ab7a466..4c835c6 100644
--- a/package.json
+++ b/package.json
@@ -1,6 +1,6 @@
 {
   "name": "docuri",
-  "version": "3.0.0",
+  "version": "3.0.1",
   "description": "Rich document ids for CouchDB",
   "main": "index.js",
   "scripts": {
diff --git a/test/arity_test.js b/test/arity_test.js
deleted file mode 100644
index d8c4a06..0000000
--- a/test/arity_test.js
+++ /dev/null
@@ -1,36 +0,0 @@
-var test = require('tap').test;
-var arity = require('..').arity;
-
-test('arity of type string', function(t) {
-  t.equal(arity('type'), 1, 'should return 1');
-  t.end();
-});
-test('arity of type/id string', function(t) {
-  t.equal(arity('type/id'), 2, 'should return 2');
-  t.end();
-});
-test('arity of type/id/subtype string', function(t) {
-  t.equal(arity('type/id/subtype'), 3, 'should return 3');
-  t.end();
-});
-test('arity of type//subtype string', function(t) {
-  t.equal(arity('type//subtype'), 3, 'should return 3');
-  t.end();
-});
-
-test('arity of type object', function(t) {
-  t.equal(arity({ type: 'type' }), 1, 'should return 1');
-  t.end();
-});
-test('arity of type/id object', function(t) {
-  t.equal(arity({ type: 'type', id: 'id'}), 2, 'should return 2');
-  t.end();
-});
-test('arity of type/id/subtype object', function(t) {
-  t.equal(arity({ type: 'type', id: 'id', subtype: 'subtype' }), 3, 'should return 3');
-  t.end();
-});
-test('arity of type//subtype object', function(t) {
-  t.equal(arity({ type: 'type', subtype: 'subtype' }), 3, 'should return 3');
-  t.end();
-});