diff --git a/phino.cabal b/phino.cabal
--- a/phino.cabal
+++ b/phino.cabal
@@ -1,7 +1,7 @@
 cabal-version:      3.0
 
 name:               phino
-version:            0.0.0.29
+version:            0.0.0.30
 license:            MIT
 synopsis:           Command-Line Manipulator of 𝜑-Calculus Expressions
 description:        Please see the README on GitHub at <https://github.com/objectionary/phino#readme>
diff --git a/src/Functions.hs b/src/Functions.hs
--- a/src/Functions.hs
+++ b/src/Functions.hs
@@ -17,6 +17,7 @@
 import Matcher
 import Misc
 import Numeric (showHex)
+import Parser (parseAttributeThrows)
 import Pretty
 import Random (randomString)
 import Regexp
@@ -118,4 +119,9 @@
   bds <- buildBindingThrows (BiMeta meta) subst
   pure (TeExpression (DataNumber (numToBts (fromIntegral (length bds)))))
 buildTermFromFunction "size" _ _ _ = throwIO (userError "Function size() requires exactly 1 meta binding")
+buildTermFromFunction "tau" [ArgExpression expr] subst prog = do
+  TeBytes bts <- buildTermFromFunction "dataize" [ArgExpression expr] subst prog
+  attr <- parseAttributeThrows (btsToUnescapedStr bts)
+  pure (TeAttribute attr)
+buildTermFromFunction "tau" _ _ _ = throwIO (userError "Function tau() requires exactly 1 argument as expression")
 buildTermFromFunction func _ _ _ = throwIO (userError (printf "Function %s() is not supported or does not exist" func))
diff --git a/src/Parser.hs b/src/Parser.hs
--- a/src/Parser.hs
+++ b/src/Parser.hs
@@ -11,6 +11,7 @@
     parseExpression,
     parseExpressionThrows,
     parseAttribute,
+    parseAttributeThrows,
     parseBinding,
     parseBytes,
   )
@@ -37,11 +38,13 @@
 data ParserException
   = CouldNotParseProgram {message :: String}
   | CouldNotParseExpression {message :: String}
+  | CouldNotParseAttribute {message :: String}
   deriving (Exception)
 
 instance Show ParserException where
   show CouldNotParseProgram {..} = printf "Couldn't parse given phi program, cause: %s" message
   show CouldNotParseExpression {..} = printf "Couldn't parse given phi program, cause: %s" message
+  show CouldNotParseAttribute {..} = printf "Couldn't parse given attribute, cause: %s" message
 
 -- White space consumer
 whiteSpace :: Parser ()
@@ -437,6 +440,11 @@
 
 parseAttribute :: String -> Either String Attribute
 parseAttribute = parse' "attribute" fullAttribute
+
+parseAttributeThrows :: String -> IO Attribute
+parseAttributeThrows attr = case parseAttribute attr of
+  Right attr' -> pure attr'
+  Left err -> throwIO (CouldNotParseAttribute err)
 
 parseExpression :: String -> Either String Expression
 parseExpression = parse' "expression" expression