diff --git a/docs/API.md b/docs/API.md
index 023bd3c4..aa0599ed 100644
--- a/docs/API.md
+++ b/docs/API.md
@@ -158,11 +158,22 @@ Return: 1 on success, 0 on error.
 
     int mg_write(struct mg_connection *, const void *buf, int len);
 
-Send data to the client. This function attempts to send all requested data,
-unlike `write()` standard library call, which might send only a portion of
-requested data.  
+Send data to the client. This function guarantees to send all requested data.
+If more then one thread is writing to the connection, writes must be
+serialized by e.g. using mutex.  
 Return: number of bytes written to the client. If return value is less then
-`len`, client has closed the connection.
+`len`, it is a failure, meaning that client has closed the connection.
+
+
+    int mg_websocket_write(struct mg_connection* conn, int opcode,
+                           const char *data, size_t data_len);
+
+Send data to a websocket client. If more then one thread is writing to the
+connection, writes must be serialized by e.g. using mutex. This function
+guarantees to send all data (semantic is similar to `mg_write()`).
+This function is available when mongoose is compiled with `-DUSE_WEBSOCKET`.  
+Return: number of bytes written to the client. If return value is less then
+`data_len`, it is a failure, meaning that client has closed the connection.
 
 
 ## Embedding Examples
diff --git a/mongoose.h b/mongoose.h
index c7098b17..031f0033 100644
--- a/mongoose.h
+++ b/mongoose.h
@@ -72,28 +72,9 @@ void mg_stop(struct mg_context *);
 
 void mg_websocket_handshake(struct mg_connection *);
 int mg_websocket_read(struct mg_connection *, int *bits, char **data);
-
-const char *mg_get_option(const struct mg_context *ctx, const char *name);
-const char **mg_get_valid_option_names(void);
-int mg_modify_passwords_file(const char *passwords_file_name,
-                             const char *domain,
-                             const char *user,
-                             const char *password);
-int mg_write(struct mg_connection *, const void *buf, int len);
-
-
-// Send data to a websocket client wrapped in a websocket frame.
-// It is unsafe to read/write to this connection from another thread.
-// This function is available when mongoose is compiled with -DUSE_WEBSOCKET
-//
-// Return:
-//  0   when the connection has been closed
-//  -1  on error
-//  >0  number of bytes written on success
 int mg_websocket_write(struct mg_connection* conn, int opcode,
                        const char *data, size_t data_len);
-
-// Opcodes, from http://tools.ietf.org/html/rfc6455
+// Websocket opcodes, from http://tools.ietf.org/html/rfc6455
 enum {
   WEBSOCKET_OPCODE_CONTINUATION = 0x0,
   WEBSOCKET_OPCODE_TEXT = 0x1,
@@ -103,6 +84,13 @@ enum {
   WEBSOCKET_OPCODE_PONG = 0xa
 };
 
+const char *mg_get_option(const struct mg_context *ctx, const char *name);
+const char **mg_get_valid_option_names(void);
+int mg_modify_passwords_file(const char *passwords_file_name,
+                             const char *domain,
+                             const char *user,
+                             const char *password);
+int mg_write(struct mg_connection *, const void *buf, int len);
 
 // Macros for enabling compiler-specific checks for printf-like arguments.
 #undef PRINTF_FORMAT_STRING