Described used IDEC extension in ii-doc.txt

ii-doc.txt

@@ -35,14 +35,23 @@ Every station must implement the following HTTP API calls.
 In case of multi-line responses, the newline separator must be "\n" character
 (line feed, ASCII 10).
 
-- Fetching the public echo list -
+- Fetching the public echo list (IDEC extension) -
 
 Request: GET /list.txt
 Response: newline-separated list of echo_name:msg_count:echo_description
 
+- Fetching the echo message count (IDEC extension) -
+
+Request: GET /x/c/echo.1.name/echo.2.name/..
+Response: newline separated list of echo_name:msg_count
+
+Note: msg_count must not decrease even if some messages are deleted.
+
 - Listing messages in the echo (s) -
 
 Request: GET /u/e/echo.1.name/echo.2.name/...
+IDEC extended syntax: GET /u/e/echo.1.name/echo.2.name/.../offset:count
+(where offset can be negative)
 Response: newline-separated list of echo names and message IDs in the format:
 
 echo.1.name
@@ -74,6 +83,15 @@ Response: in case of success, must start with "msg ok"
 where base64_msgtext is the Base64-encoded Point-to-Node Message (see below).
 The maximum length of the tmsg field must be 87382 bytes.
 
+- Listing IDEC features (IDEC extension) -
+
+Request: GET /x/features
+Response: newline-separated list of supported non-standard URL paths
+(x/c, u/e, /list.txt etc)
+
+Note: if the /x/features path is unavailable, the client must assume that no
+IDEC extensions except /list.txt are supported by the server.
+
 Node-to-Point Message format
 ----------------------------
 The encoding must be UTF-8 and the newline separator must be "\n" (ASCII 10).