diff --git a/src/hz_aaci.erl b/src/hz_aaci.erl
index 90ec5bc..5011e29 100644
--- a/src/hz_aaci.erl
+++ b/src/hz_aaci.erl
@@ -25,11 +25,43 @@
 
 %%% Types
 
--export_type([aaci/0]).
+-export_type([aaci/0, annotated_type/0, erlang_repr/0]).
 
 -include_lib("eunit/include/eunit.hrl").
 
--type aaci() :: {aaci, term(), term(), term()}.
+-type aaci() :: {aaci, string(), #{string() => function_spec()}, #{string() => typedef()}}.
+-type function_spec() :: {[{string(), annotated_type()}], annotated_type()}.
+-type typedef() :: {[string()], typedef_rhs()}.
+
+-type annotated_type() :: {opaque_type(), already_normalized | opaque_type(), builtin_type(annotated_type())}.
+-type builtin_type(T) ::   {bytes, [integer() | any]}
+                         | {record, [{string(), T}]}
+                         | {variant, [{string(), [T]}]}
+                         | {tuple, [T]}
+                         | {list, [T]}
+                         | {map, [T]}
+                         | integer
+                         | boolean
+                         | bits
+                         | char
+                         | string
+                         | address
+                         | signature
+                         | contract
+                         | channel
+                         | unknown_type.
+
+-type opaque_type() :: string() | {string(), [opaque_type()]} | builtin_type(opaque_type()).
+
+-type typedef_rhs() :: {var, string()} | string() | {string(), [opaque_type()]} | builtin_type(typedef_rhs()).
+
+-type erlang_repr() ::   integer()
+                       | string()
+                       | boolean()
+                       | binary()
+                       | tuple() % Tuples, variants, or raw addresses
+                       | [erlang_repr()]
+                       | #{erlang_repr() => erlang_repr()}.
 
 %%% ACI/AACI
 
@@ -47,6 +79,9 @@ prepare_from_file(Path) ->
         Error               -> Error
     end.
 
+-spec prepare(ACI) -> AACI
+    when ACI  :: term(),
+         AACI :: aaci().
 
 prepare(ACI) ->
     % We want to take the types represented by the ACI, things like N1.T(N2.T),
@@ -66,6 +101,12 @@ prepare(ACI) ->
 
     {aaci, Name, Specs, TypeDefs}.
 
+-spec convert_aci_types(ACI) -> {Name, OpaqueSpecs, TypeDefs}
+    when ACI         :: term(),
+         Name        :: string(),
+         OpaqueSpecs :: [{string(), [{string(), opaque_type()}], opaque_type()}],
+         TypeDefs    :: #{string() => typedef()}.
+
 convert_aci_types(ACI) ->
     % Find the main contract, so we can get the specifications of its
     % entrypoints.
@@ -134,6 +175,12 @@ convert_typedefs_loop([Next | Rest], NamePrefix, Converted) ->
     Def = opaque_type(Params, DefACI),
     convert_typedefs_loop(Rest, NamePrefix, [Converted, {Name, Params, Def}]).
 
+-spec collect_opaque_types(Tree, TypeDefs) -> TypeDefs
+    when Tree     :: typedef_tree(),
+         TypeDefs :: #{string() => typedef()}.
+
+-type typedef_tree() :: {string(), [string()], typedef_rhs()} | list(typedef_tree()).
+
 collect_opaque_types([], Types) ->
     Types;
 collect_opaque_types([L | R], Types) ->
@@ -144,6 +191,11 @@ collect_opaque_types({Name, Params, Def}, Types) ->
 
 %%% ACI Type -> Opaque Type
 
+-spec opaque_type(Params, ACIType) -> Opaque
+    when Params  :: [string()],
+         ACIType :: binary() | map(),
+         Opaque  :: typedef_rhs().
+
 % Convert an ACI type defintion/spec into the 'opaque type' representation that
 % our dereferencing algorithms can reason about.
 opaque_type(Params, NameBin) when is_binary(NameBin) ->
@@ -171,6 +223,8 @@ opaque_type(Params, Pair) when is_map(Pair) ->
     [{Name, TypeArgs}] = maps:to_list(Pair),
     {opaque_type_name(Name), [opaque_type(Params, Arg) || Arg <- TypeArgs]}.
 
+-spec opaque_type_name(binary()) -> atom() | string().
+
 % Atoms for any builtins that aren't qualified by a namespace in Sophia.
 % Everything else stays as a string, user-defined or not.
 opaque_type_name(<<"int">>)       -> integer;
@@ -280,6 +334,12 @@ annotate_function_specs([{Name, ArgsOpaque, ResultOpaque} | Rest], Types, Specs)
     NewSpecs = maps:put(Name, {Args, Result}, Specs),
     annotate_function_specs(Rest, Types, NewSpecs).
 
+-spec annotate_type(Opaque, Types) -> {ok, Annotated} | {error, Reason}
+    when Opaque    :: opaque_type(),
+         Types     :: #{string() => typedef()},
+         Annotated :: annotated_type(),
+         Reason    :: none().
+
 annotate_type(T, Types) ->
     case normalize_opaque_type(T, Types) of
         {ok, AlreadyNormalized, NOpaque, NExpanded} ->
@@ -445,6 +505,14 @@ substitute_opaque_types(Bindings, Types) ->
 
 %%% Erlang to FATE
 
+-spec erlang_args_to_fate(VarTypes, Terms) -> {ok, FATE} | {error, Errors}
+    when VarTypes :: [{string(), annotated_type()}],
+         Terms    :: [erlang_repr()],
+         FATE     :: gmb_fate_data:fate_type(),
+         Errors   :: [{Reason, [PathStep]}],
+         Reason   :: term(),
+         PathStep :: term().
+
 erlang_args_to_fate(VarTypes, Terms) ->
     DefLength = length(VarTypes),
     ArgLength = length(Terms),
@@ -454,6 +522,14 @@ erlang_args_to_fate(VarTypes, Terms) ->
         DefLength   < ArgLength -> {error, too_many_args}
     end.
 
+-spec erlang_to_fate(Type, Erlang) -> {ok, FATE} | {error, Errors}
+    when Type     :: annotated_type(),
+         FATE     :: gmb_fate_data:fate_type(),
+         Erlang   :: erlang_repr(),
+         Errors   :: [{Reason, [PathStep]}],
+         Reason   :: term(),
+         PathStep :: term().
+
 erlang_to_fate({_, _, integer}, S) when is_integer(S) ->
     {ok, S};
 erlang_to_fate({O, N, integer},  S) when is_list(S) ->
@@ -794,6 +870,14 @@ coerce_direction(Type, Term, to_fate) ->
 coerce_direction(Type, Term, from_fate) ->
     fate_to_erlang(Type, Term).
 
+-spec fate_to_erlang(Type, FATE) -> {ok, Erlang} | {error, Errors}
+    when Type     :: annotated_type(),
+         FATE     :: gmb_fate_data:fate_type(),
+         Erlang   :: erlang_repr(),
+         Errors   :: [{Reason, [PathStep]}],
+         Reason   :: term(),
+         PathStep :: term().
+
 fate_to_erlang({_, _, integer}, S) when is_integer(S) ->
     {ok, S};
 fate_to_erlang({_, _, address}, {address, Bin}) ->
diff --git a/src/hz_sophia.erl b/src/hz_sophia.erl
index 4c1c8cb..2df3755 100644
--- a/src/hz_sophia.erl
+++ b/src/hz_sophia.erl
@@ -10,14 +10,20 @@
 -include_lib("eunit/include/eunit.hrl").
 
 
--spec parse_literal(String) -> Result
-    when String :: string(),
-         Result :: {ok, gmb_fate_data:fate_type()}
-                 | {error, Reason :: term()}.
+-spec parse_literal(Sophia) -> {ok, FATE} | {error, Reason}
+    when Sophia :: string(),
+         FATE   :: gmb_fate_data:fate_type(),
+         Reason :: term().
 
 parse_literal(String) ->
     parse_literal(unknown_type(), String).
 
+-spec parse_literal(Type, Sophia) -> {ok, FATE} | {error, Reason}
+    when Type :: hz_aaci:annotated_type(),
+         Sophia :: string(),
+         FATE   :: gmb_fate_data:fate_type(),
+         Reason :: term().
+
 parse_literal(Type, String) ->
     case parse_expression(Type, {1, 1}, String) of
         {ok, {Result, NewPos, NewString}} ->
@@ -917,16 +923,34 @@ wrap_error(Reason, _) -> Reason.
 
 %%% Pretty Printing
 
+-spec fate_to_list(FATE) -> Sophia
+    when FATE   :: gmb_fate_data:fate_type(),
+         Sophia :: string().
+
 fate_to_list(Term) ->
     fate_to_list(unknown_type(), Term).
 
+-spec fate_to_list(Type, FATE) -> Sophia
+    when Type   :: hz_aaci:annotated_type(),
+         FATE   :: gmb_fate_data:fate_type(),
+         Sophia :: string().
+
 fate_to_list(Type, Term) ->
     IOList = fate_to_iolist(Type, Term),
     unicode:characters_to_list(IOList).
 
+-spec fate_to_iolist(FATE) -> Sophia
+    when FATE   :: gmb_fate_data:fate_type(),
+         Sophia :: iolist().
+
 fate_to_iolist(Term) ->
     fate_to_iolist(unknown_type(), Term).
 
+-spec fate_to_iolist(Type, FATE) -> Sophia
+    when Type   :: hz_aaci:annotated_type(),
+         FATE   :: gmb_fate_data:fate_type(),
+         Sophia :: iolist().
+
 % Special case for singleton records, since they are erased during compilation.
 fate_to_iolist({_, _, {record, [{FieldName, FieldType}]}}, Term) ->
     singleton_record_to_iolist(FieldName, FieldType, Term);
@@ -1430,6 +1454,6 @@ singleton_test() ->
 
     % Also if we wanted an integer, the singleton is NOT dropped, so is also an
     % error.
-    {error, {expected_close_paren, 1, 3}} = parse_literal({integer, alread_normalized, integer}, "(1,)"),
+    {error, {expected_close_paren, 1, 3}} = parse_literal({integer, already_normalized, integer}, "(1,)"),
 
     ok.