diff --git a/mempool/docs/README.md b/mempool/docs/README.md
index 075bafede..3ad1213ba 100644
--- a/mempool/docs/README.md
+++ b/mempool/docs/README.md
@@ -6,6 +6,6 @@ of the mempool module.
 Components:
 
 * [Config](./config.md) - how to configure it
-* [Functionality](./functionality.md) - high-level description of the functionality it provides
 * [External Messages](./messages.md) - The messages we accept over p2p and rpc interfaces
+* [Functionality](./functionality.md) - high-level description of the functionality it provides
 * [Local Services](./services.md) - Interfaces with consensus and abci services
diff --git a/mempool/docs/messages.md b/mempool/docs/messages.md
new file mode 100644
index 000000000..5bd1d1e55
--- /dev/null
+++ b/mempool/docs/messages.md
@@ -0,0 +1,60 @@
+# Mempool Messages
+
+## P2P Messages
+
+There is currently only one message that Mempool broadcasts
+and receives over the p2p gossip network (via the reactor):
+`TxMessage`
+
+```go
+// TxMessage is a MempoolMessage containing a transaction.
+type TxMessage struct {
+    Tx types.Tx
+}
+```
+
+TxMessage is go-wire encoded and prepended with `0x1` as a
+"type byte". This is followed by a go-wire encoded byte-slice.
+Prefix of 40=0x28 byte tx is: `0x010128...` followed by
+the actual 40-byte tx. Prefix of 350=0x015e byte tx is:
+`0x0102015e...` followed by the actual 350 byte tx.
+
+(Please see the [go-wire repo](https://github.com/tendermint/go-wire#an-interface-example) for more information)
+
+## RPC Messages
+
+Mempool exposes `CheckTx([]byte)` over the RPC interface.
+
+It can be posted via `broadcast_commit`, `broadcast_sync` or
+`broadcast_async`. They all parse a message with one argument,
+`"tx": "HEX_ENCODED_BINARY"` and differ in only how long they
+wait before returning (sync makes sure CheckTx passes, commit
+makes sure it was included in a signed block).
+
+Request (`POST http://gaia.zone:46657/`):
+```json
+{
+ "id": "",
+ "jsonrpc": "2.0",
+ "method": "broadcast_sync",
+ "params": {
+    "tx": "F012A4BC68..."
+ }
+}
+```
+
+
+Response:
+```json
+{
+ "error": "",
+ "result": {
+     "hash": "E39AAB7A537ABAA237831742DCE1117F187C3C52",
+     "log": "",
+     "data": "",
+     "code": 0
+ },
+ "id": "",
+ "jsonrpc": "2.0"
+}
+```