diff --git a/README.md b/README.md
index 2ae1a61..e8bcce5 100644
--- a/README.md
+++ b/README.md
@@ -25,26 +25,37 @@ const cool = mux.addProtocol({
     major: 1,
     minor: 0
   },
-  // an array of compact encoders, each encoding/decoding the messages sent
-  messages: [
-    c.string,
-    c.bool
-  ],
+  messages: 2, // protocol has 2 messages
   onremoteopen () {
     console.log('the other side opened this protocol!')
   },
-  onemoteclose () {
+  onremoteclose () {
     console.log('the other side closed this protocol!')
-  },
-  onmessage (type, message) {
-    console.log('the other side sent a message', type, message)
   }
 })
 
-// And send some messages
+// And add some messages
 
-cool.send(0, 'a string')
-cool.send(1, true)
+const one = cool.addMessage({
+  type: 0,
+  encoding: c.string,
+  onmessage (m) {
+    console.log('recv message (1)', m)
+  }
+})
+
+const two = cool.addMessage({
+  type: 1,
+  encoding: c.bool,
+  onmessage (m) {
+    console.log('recv message (2)', m)
+  }
+})
+
+// And send some data
+
+one.send('a string')
+two.send(true)
 ```
 
 ## API
@@ -87,31 +98,50 @@ Options include:
     major: 0,
     minor: 0
   },
-  // Array of the message types you want to send/receive. Should be compact-encoders
-  messages: [
-    ...
-  ],
+  // Number of messages types you want to send/receive.
+  messages: 2,
   // Called when the remote side adds this protocol.
   // Errors here are caught and forwared to stream.destroy
   async onremoteopen () {},
   // Called when the remote side closes or rejects this protocol.
   // Errors here are caught and forwared to stream.destroy
-  async onremoteclose () {},
-  // Called when the remote sends a message
-  // Errors here are caught and forwared to stream.destroy
-  async onmessage (type, message) {}
+  async onremoteclose () {}
 }
 ```
 
 Each of the functions can also be set directly on the instance with the same name.
 
+#### `const m = p.addMessage(opts)`
+
+Specify a message. Options include:
+
+``` js
+{
+  // Defaults to an incrementing number
+  type: numericIndex,
+  // compact-encoding specifying how to encode/decode this message
+  encoding: c.binary,
+  // Called when the remote side sends a message.
+  // Errors here are caught and forwared to stream.destroy
+  async onmessage (message) { }
+}
+```
+
+#### `m.send(data)`
+
+Send a message.
+
+#### `m.onmessage`
+
+Function that is called when a message arrives.
+
+#### `m.encoding`
+
+The encoding for this message.
+
 #### `p.close()`
 
-Closes the protocol
-
-#### `p.send(type, message)`
-
-Send a message, type is the offset into the messages array.
+Closes the protocol.
 
 #### `p.cork()`
 
diff --git a/index.js b/index.js
index 8741416..fc9505f 100644
--- a/index.js
+++ b/index.js
@@ -8,12 +8,15 @@ const EMPTY = []
 class Protocol {
   constructor (mux) {
     this.mux = mux
+
     this.name = null
     this.version = null
     this.messages = EMPTY
+    this.context = null
     this.offset = 0
     this.length = 0
     this.opened = false
+    this.corked = false
 
     this.remoteVersion = null
     this.remoteOffset = 0
@@ -21,29 +24,49 @@ class Protocol {
     this.remoteOpened = false
     this.remoteClosed = false
 
-    this.onmessage = noop
     this.onremoteopen = noop
     this.onremoteclose = noop
   }
 
-  _attach ({ name, version = { major: 0, minor: 0 }, messages, onmessage = noop, onremoteopen = noop, onremoteclose = noop }) {
+  _attach ({ name, version = { major: 0, minor: 0 }, messages = 0, context = null, onremoteopen = noop, onremoteclose = noop }) {
     const opened = this.opened
 
     this.name = name
     this.version = version
-    this.messages = messages
+    this.messages = new Array(messages)
+    this.context = context
     this.offset = this.mux.offset
-    this.length = messages.length
+    this.length = messages
     this.opened = true
     this.corked = false
 
-    this.onmessage = onmessage
     this.onremoteopen = onremoteopen
     this.onremoteclose = onremoteclose
 
     return !opened
   }
 
+  _nextMessage () {
+    for (let i = this.messages.length - 1; i >= 0; i--) {
+      if (this.messages[i] === undefined && (i === 0 || this.messages[i - 1] !== undefined)) {
+        return i
+      }
+    }
+    return -1
+  }
+
+  addMessage ({ type = this._nextMessage(), encoding = c.binary, onmessage = noop } = {}) {
+    if (type < 0 || type >= this.messages.length) {
+      throw new Error('Invalid type, must be <= ' + this.messages.length)
+    }
+
+    const t = this.offset + type
+    const send = (message) => this.opened && this.mux._push(t, m.encoding, message)
+    const m = this.messages[type] = { encoding, onmessage, send }
+
+    return m
+  }
+
   cork () {
     if (this.corked) return
     this.corked = true
@@ -56,15 +79,6 @@ class Protocol {
     this.mux.uncork()
   }
 
-  send (type, message) {
-    if (!this.opened) return false
-
-    const t = this.offset + type
-    const m = this.messages[type]
-
-    return this.mux._push(t, m, message)
-  }
-
   close () {
     if (this.opened === false) return
     this.opened = false
@@ -76,7 +90,7 @@ class Protocol {
     this.messages = EMPTY
     this.offset = 0
     this.length = 0
-    this.onmessage = this.onremoteopen = this.onremoteclose = noop
+    this.onremoteopen = this.onremoteclose = noop
     this.mux._push(2, c.uint, offset)
     this._gc()
 
@@ -92,9 +106,7 @@ class Protocol {
     if (type >= this.messages.length) return
 
     const m = this.messages[type]
-    const message = m.decode(state)
-
-    this.mux._catch(this.onmessage(type, message))
+    if (m !== undefined) this.mux._catch(m.onmessage(m.encoding.decode(state), this.context))
   }
 }
 
diff --git a/test.js b/test.js
index 180bdd5..6ecc90f 100644
--- a/test.js
+++ b/test.js
@@ -9,69 +9,72 @@ test('basic', function (t) {
 
   replicate(a, b)
 
-  a.addProtocol({
+  const p = a.addProtocol({
     name: 'foo',
-    messages: [c.string],
+    messages: 1,
     onremoteopen () {
       t.pass('a remote opened')
-    },
-    onmessage (type, message) {
-      t.is(type, 0)
+    }
+  })
+
+  p.addMessage({
+    encoding: c.string,
+    onmessage (message) {
       t.is(message, 'hello world')
     }
   })
 
   const bp = b.addProtocol({
     name: 'foo',
-    messages: [c.string]
+    messages: 1
   })
 
-  t.plan(3)
+  t.plan(2)
 
-  bp.send(0, 'hello world')
+  bp.addMessage({ encoding: c.string }).send('hello world')
 })
 
 test('echo message', function (t) {
   const a = new Protomux(new SecretStream(true))
-
-  const b = new Protomux(new SecretStream(false), [{
-    name: 'other',
-    messages: [c.bool, c.bool]
-  }, {
-    name: 'foo',
-    messages: [c.string]
-  }])
+  const b = new Protomux(new SecretStream(false))
 
   replicate(a, b)
 
   const ap = a.addProtocol({
     name: 'foo',
-    messages: [c.string],
-    onmessage (type, message) {
-      ap.send(type, 'echo: ' + message)
+    messages: 1
+  })
+
+  const aEcho = ap.addMessage({
+    encoding: c.string,
+    onmessage (message) {
+      aEcho.send('echo: ' + message)
     }
   })
 
   b.addProtocol({
     name: 'other',
-    messages: [c.bool, c.bool]
+    messages: 2
   })
 
   const bp = b.addProtocol({
     name: 'foo',
-    messages: [c.string],
+    messages: 1,
     onremoteopen () {
       t.pass('b remote opened')
-    },
-    onmessage (type, message) {
-      t.is(type, 0)
+    }
+  })
+
+  const bEcho = bp.addMessage({
+    encoding: c.string,
+    onmessage (message) {
       t.is(message, 'echo: hello world')
     }
   })
 
-  t.plan(3)
+  t.plan(2)
 
-  bp.send(0, 'hello world')
+  bEcho.send('hello world')
 })
 
 test('multi message', function (t) {
@@ -79,38 +82,47 @@ test('multi message', function (t) {
 
   a.addProtocol({
     name: 'other',
-    messages: [c.bool, c.bool]
+    messages: 2
   })
 
   const ap = a.addProtocol({
     name: 'multi',
-    messages: [c.int, c.string, c.string]
+    messages: 3
   })
 
+  const a1 = ap.addMessage({ encoding: c.int })
+  const a2 = ap.addMessage({ encoding: c.string })
+  const a3 = ap.addMessage({ encoding: c.string })
+
   const b = new Protomux(new SecretStream(false))
 
   const bp = b.addProtocol({
     name: 'multi',
-    messages: [c.int, c.string]
+    messages: 2
   })
 
+  const b1 = bp.addMessage({ encoding: c.int })
+  const b2 = bp.addMessage({ encoding: c.string })
+
   replicate(a, b)
 
-  t.plan(4)
+  t.plan(2)
 
-  ap.send(0, 42)
-  ap.send(1, 'a string with 42')
-  ap.send(2, 'should be ignored')
+  a1.send(42)
+  a2.send('a string with 42')
+  a3.send('should be ignored')
 
   const expected = [
-    [0, 42],
-    [1, 'a string with 42']
+    42,
+    'a string with 42'
   ]
 
-  bp.onmessage = function (type, message) {
-    const e = expected.shift()
-    t.is(type, e[0])
-    t.is(message, e[1])
+  b1.onmessage = function (message) {
+    t.is(message, expected.shift())
+  }
+
+  b2.onmessage = function (message) {
+    t.is(message, expected.shift())
   }
 })
 
@@ -121,36 +133,42 @@ test('corks', function (t) {
 
   a.addProtocol({
     name: 'other',
-    messages: [c.bool, c.bool]
+    messages: 2
   })
 
   const ap = a.addProtocol({
     name: 'multi',
-    messages: [c.int, c.string]
+    messages: 2
   })
 
+  const a1 = ap.addMessage({ encoding: c.int })
+  const a2 = ap.addMessage({ encoding: c.string })
+
   const b = new Protomux(new SecretStream(false))
 
   const bp = b.addProtocol({
     name: 'multi',
-    messages: [c.int, c.string]
+    messages: 2
   })
 
+  const b1 = bp.addMessage({ encoding: c.int })
+  const b2 = bp.addMessage({ encoding: c.string })
+
   replicate(a, b)
 
-  t.plan(8 + 1)
+  t.plan(4 + 1)
 
   const expected = [
-    [0, 1],
-    [0, 2],
-    [0, 3],
-    [1, 'a string']
+    1,
+    2,
+    3,
+    'a string'
   ]
 
-  ap.send(0, 1)
-  ap.send(0, 2)
-  ap.send(0, 3)
-  ap.send(1, 'a string')
+  a1.send(1)
+  a1.send(2)
+  a1.send(3)
+  a2.send('a string')
 
   a.uncork()
 
@@ -158,10 +176,12 @@ test('corks', function (t) {
     t.ok(expected.length === 0, 'received all messages in one data packet')
   })
 
-  bp.onmessage = function (type, message) {
-    const e = expected.shift()
-    t.is(type, e[0])
-    t.is(message, e[1])
+  b1.onmessage = function (message) {
+    t.is(message, expected.shift())
+  }
+
+  b2.onmessage = function (message) {
+    t.is(message, expected.shift())
   }
 })