diff --git a/app/Main.hs b/app/Main.hs
index 9afa44a..b3ed9ca 100644
--- a/app/Main.hs
+++ b/app/Main.hs
@@ -11,6 +11,7 @@ import Tempered.Options
 import Tempered.Parser
 import Tempered.Template
 
+-- | Run tempered on cmdline args.
 main :: IO ()
 main = do
   envVars <- getEnvVars
@@ -20,6 +21,7 @@ main = do
   where
     renderOutput = traverse_ (interpTemplate  >=> liftIO . putStr)
 
+-- | Combine local and global environment variables
 getEnvVars :: IO EnvVars
 getEnvVars = do
   cwd <- getCurrentDirectory
diff --git a/src/Tempered/Options.hs b/src/Tempered/Options.hs
index 6bfbdad..a886158 100644
--- a/src/Tempered/Options.hs
+++ b/src/Tempered/Options.hs
@@ -18,25 +18,29 @@ import System.Exit
 type EnvVars = [(String, String)]
 type EnvMap = M.Map String String
 
+-- | Given a directory tries to find env.yaml recursively upwards;
+-- parses `EnvMap` from the file if found.
 getProjectOptions :: FilePath -> IO EnvMap
 getProjectOptions path = do
   mProjSettingsFile <- findProjSettings path
   mOptions <- traverse optionsFromFilename mProjSettingsFile
   return $ fromMaybe mempty mOptions
 
--- Retrieve an options object from a yaml file
+-- Retrieve an EnvMap from a yaml file
 optionsFromFilename :: FilePath -> IO EnvMap
 optionsFromFilename = Y.decodeFileEither >=>
   \case
     Left err -> die . prettyPrintParseException $ err
     Right options -> return options
 
+-- Try to find an 'env.yaml' file.
 findProjSettings :: FilePath -> IO (Maybe FilePath)
 findProjSettings fpath = do
   absPath <- makeAbsolute fpath
   let searchPaths = (</> "env.yaml") <$> recurseUp absPath
   listToMaybe <$> filterM doesFileExist searchPaths
 
+-- Get all parent directories of a directory path.
 recurseUp :: FilePath -> [FilePath]
 recurseUp = unfoldr go
   where
diff --git a/src/Tempered/Parser.hs b/src/Tempered/Parser.hs
index 052de9b..ca2b80b 100644
--- a/src/Tempered/Parser.hs
+++ b/src/Tempered/Parser.hs
@@ -17,18 +17,22 @@ infix 0 ?>
 (?>) :: String -> ParsecT s u m a -> ParsecT s u m a
 (?>) = flip (<?>)
 
+-- | Parse a template from a file.
 templateFromFile :: FilePath -> IO (Either ParseError (Template Command))
 templateFromFile fname = do
   file <- readFile fname
   return $ parseTemplate fname file
 
+-- | Parse a template from a string with a given filename for errors.
 parseTemplate :: FilePath -> String -> Either ParseError (Template Command)
 parseTemplate = runP templateP ()
 
+-- | Fail if parsing errors occurred, otherwise return the template.
 handleTemplateError :: Either ParseError (Template a) -> IO (Template a)
 handleTemplateError (Left err) = print err >> exitFailure
 handleTemplateError (Right temp) = return temp
 
+-- | Template Parser
 templateP :: Parser (Template Command)
 templateP = "template" ?> do
   optional (try shebangP)
@@ -39,10 +43,12 @@ templateP = "template" ?> do
       cmd = Right <$> commandP
       txt = Left <$> many1 (notFollowedBy (string "{{") *> anyChar)
 
+-- | Shebang Parser
 shebangP :: Parser String
 shebangP = "shebang" ?>
   liftA2 (++) (lookAhead (string "#!") *> string "#!") (manyTill anyChar (char '\n'))
 
+-- | Command Parser
 commandP :: Parser Command
 commandP = "command" ?> do
   _ <- string "{{"
diff --git a/src/Tempered/Template.hs b/src/Tempered/Template.hs
index 86d46bf..08a4ae0 100644
--- a/src/Tempered/Template.hs
+++ b/src/Tempered/Template.hs
@@ -13,19 +13,23 @@ import Data.Foldable
 
 import Tempered.Options
 
+-- | Represents values interspersed with text.
 data Template a =
   Template [Either String a]
   deriving Show
 
+-- | Given an execution environment render a template into a string.
 interpTemplate :: (MonadReader EnvVars m, MonadIO m) => Template Command -> m String
 interpTemplate (Template elems) = fold <$> mapM toText elems
     where
       toText = either return interpCommand
 
+-- | Represents a command to be run by the system.
 data Command =
   Command String
   deriving Show
 
+-- | Run a command in an environment returning the result.
 interpCommand :: (MonadReader EnvVars m, MonadIO m) => Command -> m String
 interpCommand (Command cmd) = do
   envVars <- ask