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+Appends the specified stream entry to the stream at the specified key. If the
+key does not exist, as a side effect of running this command the key is created
+with a stream value.
+
+An entry is composed of a set of field-value pairs, it is basically a small
+dictionary. The field-value pairs are stored in the same order they are given by
+the user, and commands to read the stream such as `XRANGE` or `XREAD` are
+guaranteed to return the fields and values exactly in the same order they were
+added by `XADD`.
+
+`XADD` is the _only Redis command_ that can add data to a stream, but there are
+other commands, such as `XDEL` and `XTRIM`, that are able to remove data from a
+stream.
+
+## Specifying a Stream ID as an argument
+
+A stream entry ID identifies a given entry inside a stream. The `XADD` command
+will auto-generate a unique ID for you if the ID argument specified is the `*`
+character (asterisk ASCII character). However, while useful only in very rare
+cases, it is possible to specify a well-formed ID, so that the new entry will be
+added exactly with the specified ID.
+
+IDs are specified by two numbers separated by a `-` character:
+
+    1526919030474-55
+
+Both quantities are 64-bit numbers. When an ID is auto-generated, the first part
+is the Unix time in milliseconds of the Redis instance generating the ID. The
+second part is just a sequence number and is used in order to distinguish IDs
+generated in the same millisecond.
+
+IDs are guaranteed to be always incremental: If you compare the ID of the entry
+just inserted it will be greater than any other past ID, so entries are totally
+ordered inside a stream. In order to guarantee this property, if the current top
+ID in the stream has a time greater than the current local time of the instance,
+the top entry time will be used instead, and the sequence part of the ID
+incremented. This may happen when, for instance, the local clock jumps backward,
+or if after a failover the new master has a different absolute time.
+
+When a user specified an explicit ID to `XADD`, the minimum valid ID is `0-1`,
+and the user _must_ specify an ID which is greater than any other ID currently
+inside the stream, otherwise the command will fail. Usually resorting to
+specific IDs is useful only if you have another system generating unique IDs
+(for instance an SQL table) and you really want the Redis stream IDs to match
+the one of this other system.
+
+## Capped streams
+
+It is possible to limit the size of the stream to a maximum number of elements
+using the **MAXLEN** option.
+
+Trimming with **MAXLEN** can be expensive compared to just adding entries with
+`XADD`: streams are represented by macro nodes into a radix tree, in order to be
+very memory efficient. Altering the single macro node, consisting of a few tens
+of elements, is not optimal. So it is possible to give the command in the
+following special form:
+
+    XADD mystream MAXLEN ~ 1000 * ... entry fields here ...
+
+The `~` argument between the **MAXLEN** option and the actual count means that
+the user is not really requesting that the stream length is exactly 1000 items,
+but instead it could be a few tens of entries more, but never less than 1000
+items. When this option modifier is used, the trimming is performed only when
+Redis is able to remove a whole macro node. This makes it much more efficient,
+and it is usually what you want.
+
+## Additional information about streams
+
+For further information about Redis streams please check our
+[introduction to Redis Streams document](/topics/streams-intro).
+
+@return
+
+@bulk-string-reply, specifically:
+
+The command returns the ID of the added entry. The ID is the one auto-generated
+if `*` is passed as ID argument, otherwise the command just returns the same ID
+specified by the user during insertion.
+
+@examples
+
+```cli
+XADD mystream * name Sara surname OConnor
+XADD mystream * field1 value1 field2 value2 field3 value3
+XLEN mystream
+XRANGE mystream - +
+```