diff --git a/src/hz_aaci.erl b/src/hz_aaci.erl
index f9da33f..8fda712 100644
--- a/src/hz_aaci.erl
+++ b/src/hz_aaci.erl
@@ -22,6 +22,8 @@
          fate_to_erlang/2,
          erlang_args_to_fate/2,
          get_function_signature/2]).
+% Internal stuff that is useful for writing AACI unit tests.
+-export([annotate_type/2]).
 
 %%% Types
 
diff --git a/src/hz_sophia.erl b/src/hz_sophia.erl
new file mode 100644
index 0000000..b428616
--- /dev/null
+++ b/src/hz_sophia.erl
@@ -0,0 +1,130 @@
+-module(hz_sophia).
+-vsn("0.8.2").
+-author("Jarvis Carroll <spiveehere@gmail.com>").
+-copyright("Jarvis Carroll <spiveehere@gmail.com>").
+-license("GPL-3.0-or-later").
+
+-include_lib("eunit/include/eunit.hrl").
+
+parse_literal(Type, String) ->
+    case parse_expression(Type, {tk, 1, 1}, String) of
+        {ok, {Result, NewTk, NewString}} ->
+            parse_literal2(Result, NewTk, NewString);
+        {error, Reason} ->
+            {error, Reason}
+    end.
+
+parse_literal2(Result, Tk, String) ->
+    % We have parsed a valid expression. Now check that the string ends.
+    case next_token(Tk, String) of
+        {ok, {{eof, _, _, _, _}, _, _}} ->
+            {ok, Result};
+        {ok, {{_, S, Row, Start, End}, _, _}} ->
+            {error, {unexpected_token, S, Row, Start, End}};
+        {error, Reason} ->
+            {error, Reason}
+    end.
+
+%%% Tokenizer
+
+next_token({tk, Row, Col}, []) ->
+    {ok, {{eof, "", Row, Col, Col}, {tk, Row, Col}, []}};
+next_token({tk, Row, Col}, " " ++ Rest) ->
+    next_token({tk, Row + 1, Col}, Rest);
+next_token({tk, Row, Col}, "\t" ++ Rest) ->
+    next_token({tk, Row + 1, Col}, Rest);
+next_token(Tk, [N | _] = String) when N >= $0, N =< $9 ->
+    num_token(Tk, Tk, String, []);
+next_token(Tk, [N | _] = String) when N >= $A, N =< $Z ->
+    alphanum_token(Tk, Tk, String, []);
+next_token(Tk, [N | _] = String) when N >= $a, N =< $z ->
+    alphanum_token(Tk, Tk, String, []);
+next_token(Tk, [$_ | _] = String) ->
+    alphanum_token(Tk, Tk, String, []);
+next_token({tk, Row, Col}, [Char | _]) ->
+    {error, {unknown_char, Row, Col, [Char]}}.
+
+num_token(Start, {tk, Row, Col}, [N | Rest], Acc) when N >= $0, N =< $9 ->
+    num_token(Start, {tk, Row + 1, Col}, Rest, [N | Acc]);
+num_token({tk, _, Start}, {tk, Row, End}, String, Acc) ->
+    NumString = lists:reverse(Acc),
+    Token = {integer, NumString, Row, Start, End},
+    {ok, {Token, {tk, Row, End}, String}}.
+
+alphanum_token(Start, {tk, Row, Col}, [C | Rest], Acc) when C >= $A, C =< $Z ->
+    alphanum_token(Start, {tk, Row, Col}, Rest, [C | Acc]);
+alphanum_token(Start, {tk, Row, Col}, [C | Rest], Acc) when C >= $a, C =< $z ->
+    alphanum_token(Start, {tk, Row, Col}, Rest, [C | Acc]);
+alphanum_token(Start, {tk, Row, Col}, [C | Rest], Acc) when C >= $0, C =< $9 ->
+    alphanum_token(Start, {tk, Row, Col}, Rest, [C | Acc]);
+alphanum_token(Start, {tk, Row, Col}, [$_ | Rest], Acc) ->
+    alphanum_token(Start, {tk, Row, Col}, Rest, [$_ | Acc]);
+alphanum_token({tk, _, Start}, {tk, Row, End}, String, Acc) ->
+    AlphaString = lists:reverse(Acc),
+    Token = {alphanum, AlphaString, Row, Start, End},
+    {ok, {Token, {tk, Row, End}, String}}.
+
+
+%%% Sophia Literal Parser
+
+%%% This parser is a simple recursive descent parser, written explicitly in
+%%% erlang.
+%%%
+%%% There are no infix operators in the subset we want to parse, so recursive
+%%% descent is fine with no special tricks, no shunting yard algorithm, no
+%%% parser generators, etc.
+%%%
+%%% If we were writing this in C then we might want to work iteratively with an
+%%% array of finite state machines, i.e. with a pushdown automaton, instead of
+%%% using recursion. This is a tried and true method of making fast parsers.
+%%% Recall, however, that the BEAM *is* a stack machine, written in C, so
+%%% rather than writing confusing iterative code in Erlang, to simulate a
+%%% pushdown automaton inside another simulated stack machine... we should just
+%%% write the recursive code, thus programming the BEAM to implement the
+%%% pushdown automaton that we want.
+
+parse_expression(Type, Tk, String) ->
+    {ok, {Token, NewTk, NewString}} = next_token(Tk, String),
+    parse_expression2(Type, NewTk, NewString, Token).
+
+parse_expression2(Type, Tk, String, {integer, S, Row, Start, End}) ->
+    Value = list_to_integer(S),
+    check_type(integer, Type, Row, Start, End, {Value, Tk, String});
+parse_expression2(_, _, _, {_, S, Row, Start, End}) ->
+    {error, {unexpected_token, S, Row, Start, End}}.
+
+check_type(Expected, {_, _, Expected}, _, _, _, Result) ->
+    {ok, Result};
+check_type(_, {_, _, unknown_type}, _, _, _, Result) ->
+    % We want it to be possible to opt out of type-checking, since FATE is
+    % dynamically typed anyway.
+    {ok, Result};
+check_type(Expected, {O, N, _}, Row, Start, End, _) ->
+    {error, {wrong_type, O, N, Expected, Row, Start, End}}.
+
+
+%%% Tests
+
+check_sophia_to_fate(Type, Sophia, Fate) ->
+    {ok, FateActual} = parse_literal(Type, Sophia),
+    case FateActual of
+        Fate ->
+            ok;
+        _ ->
+            erlang:error({to_fate_failed, Fate, FateActual})
+    end.
+
+check_parser(Type, Sophia, Fate) ->
+    UnknownType = setelement(3, Type, unknown_type),
+    check_sophia_to_fate(Type, Sophia, Fate),
+    check_sophia_to_fate(UnknownType, Sophia, Fate),
+
+    % Finally, check that the FATE result is something that gmb understands.
+    gmb_fate_encoding:serialize(Fate),
+
+    ok.
+
+int_test() ->
+    {ok, Type} = hz_aaci:annotate_type(integer, #{}),
+    check_parser(Type, "123", 123).
+