diff --git a/lisp/ob-lua.el b/lisp/ob-lua.el
index 81521d9e0..dd02d6aee 100644
--- a/lisp/ob-lua.el
+++ b/lisp/ob-lua.el
@@ -82,7 +82,7 @@ This will typically be `lua-mode'."
   :type 'symbol)
 
 (defun org-babel-execute:lua (body params)
-  "Execute a block of Lua code with Babel.
+  "Execute Lua BODY according to PARAMS.
 This function is called by `org-babel-execute-src-block'."
   (let* ((session (org-babel-lua-initiate-session
 		   (cdr (assq :session params))))
@@ -129,7 +129,8 @@ VARS contains resolved variable references."
 ;; helper functions
 
 (defun org-babel-variable-assignments:lua (params)
-  "Return a list of Lua statements assigning the block's variables."
+  "Return a list of Lua statements assigning the block's variables.
+The variable definitions are defining in PARAMS."
   (mapcar
    (lambda (pair)
      (format "%s=%s"
@@ -176,6 +177,7 @@ Emacs-lisp table, otherwise return the results as a string."
   (cdr (assoc session org-babel-lua-buffers)))
 
 (defun org-babel-lua-with-earmuffs (session)
+  "Return buffer name for SESSION, as *SESSION*."
   (let ((name (if (stringp session) session (format "%s" session))))
     (if (and (string= "*" (substring name 0 1))
 	     (string= "*" (substring name (- (length name) 1))))
@@ -183,6 +185,7 @@ Emacs-lisp table, otherwise return the results as a string."
       (format "*%s*" name))))
 
 (defun org-babel-lua-without-earmuffs (session)
+"Remove stars around *SESSION*, leaving SESSION."
   (let ((name (if (stringp session) session (format "%s" session))))
     (if (and (string= "*" (substring name 0 1))
 	     (string= "*" (substring name (- (length name) 1))))
@@ -281,7 +284,11 @@ fd:close()")
 
 (defun org-babel-lua-evaluate
     (session body &optional result-type result-params preamble)
-  "Evaluate BODY as Lua code."
+  "Evaluate BODY in SESSION as Lua code.
+RESULT-TYPE and RESULT-PARAMS are passed to
+`org-babel-lua-evaluate-session' or
+`org-babel-lua-evaluate-external-process'.
+PREAMBLE is passed to `org-babel-lua-evaluate-external-process'."
   (if session
       (org-babel-lua-evaluate-session
        session body result-type result-params)
@@ -290,10 +297,12 @@ fd:close()")
 
 (defun org-babel-lua-evaluate-external-process
     (body &optional result-type result-params preamble)
-  "Evaluate BODY in external lua process.
+  "Evaluate BODY in external Lua process.
 If RESULT-TYPE equals `output' then return standard output as a
 string.  If RESULT-TYPE equals `value' then return the value of the
-last statement in BODY, as elisp."
+last statement in BODY, as elisp.
+RESULT-PARAMS list all the :result header arg parameters.
+PREAMBLE string is appended to BODY."
   (let ((raw
          (pcase result-type
            (`output (org-babel-eval org-babel-lua-command
@@ -399,7 +408,7 @@ fd:close()"
         (org-babel-lua-table-or-string results)))))
 
 (defun org-babel-lua-read-string (string)
-  "Strip single quotes from around Lua string."
+  "Strip single quotes from around Lua STRING."
   (org-unbracket-string "'" "'" string))
 
 (provide 'ob-lua)