diff --git a/compiler/Language/Elm/DevTools.hs b/compiler/Language/Elm/DevTools.hs
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+{- | This module aims to make it easier to create dev tools for Elm.
+
+     It provides the ability to:
+
+       * Detect problems in a program
+       * Figure out types of particular expressions
+       * Canonicalize variables
+       * Convert expressions to JS and HTML
+
+     This module gives limeted access to the structure of an Elm Program.
+     Giving full access would expose many internal details that are likely to
+     change as Elm progresses. These details have been hidden to avoid breaking
+     changes.
+-}
+module Language.Elm.DevTools where
+
+data Program
+
+-- | Parse an Elm program into an AST.
+parse :: String -> Either [Problem] Program
+
+-- | Get the type of a region of the program. Lets you look
+--   up the type of particular values and expressions.
+typeOf :: Program -> Region -> Either [Problem] String
+
+-- | Canonicalize a variable. So in a normal module `map` would be canonicalized
+--   to `List.map`.
+canonicalize :: Program -> Region -> [String]
+
+-- | Any problem that may come up while parsing or typing a program.
+--   All problems come with a region that is causing the problem.
+data Problem = Problem { message :: String, region :: Region }
+
+type Row = Int
+type Column = Int
+
+-- | Represents a region, spanning two points in the source code.
+data Region = Region { start :: (Row,Column), end :: (Row,Column) }
+
+-- | Takes a specific point in the source code, such as the cursor position.
+--   It then determines the region that best represents that point. When the
+--   cursor is within a variable, it chooses the variable. When the cursor is
+--   on parentheses, it selects the region within the parentheses. When the
+--   cursor is on keywords like let, it chooses the whole let-expression.
+region :: (Row,Column) -> Region
+region pos = Region pos pos