diff --git a/src/hz.erl b/src/hz.erl
index 8756608..7a72fac 100644
--- a/src/hz.erl
+++ b/src/hz.erl
@@ -662,9 +662,10 @@ dry_run(TX, Accounts, KBHash) ->
     request("/v3/dry_run", JSON).
 
 
-dry_run_map(Map) ->
-    JSON = zj:binary_encode(Map),
-    request("/v3/dry_run", JSON).
+% TODO
+%dry_run_map(Map) ->
+%    JSON = zj:binary_encode(Map),
+%    request("/v3/dry_run", JSON).
 
 
 -spec decode_bytearray_fate(EncodedStr) -> {ok, Result} | {error, Reason}
@@ -1643,6 +1644,14 @@ convert([], [], _, Terms, []) ->
 convert([], [], _, _, Errors) ->
     {error, Errors}.
 
+-spec sign_tx(Unsigned, SecKey) -> Result
+    when Unsigned :: string(),
+         SecKey   :: binary(),
+         Result   :: {ok, SignedTX} | {error, Reason}
+         SignedTX :: binary(),
+         Reason   :: chain_error().
+%% @doc
+%% Signs transaction data with the provided secret key for the currently selected network.
 
 sign_tx(Unsigned, SecKey) ->
     case network_id() of
@@ -1650,6 +1659,15 @@ sign_tx(Unsigned, SecKey) ->
         Error           -> Error
     end.
 
+
+-spec sign_tx(Unsigned, SecKey, NetworkID) -> SignedTX
+    when Unsigned  :: string(),
+         SecKey    :: binary(),
+         NetworkID :: string(),
+         SignedTX  :: binary().
+%% @doc
+%% Signs transaction data with the provided secret key using the provided network ID.
+
 sign_tx(Unsigned, SecKey, MNetworkID) ->
     UnsignedBin = unicode:characters_to_binary(Unsigned),
     NetworkID   = unicode:characters_to_binary(MNetworkID),
@@ -1669,10 +1687,21 @@ sign_tx(Unsigned, SecKey, MNetworkID) ->
     gmser_api_encoder:encode(transaction, SignedTX).
 
 
-spend(SenderID, SecKey, ReceipientID, Amount, Payload) ->
+-spec spend(SenderID, SecKey, RecipientID, Amount, Payload) -> {ok, Result} | {error, Reason}
+    when SenderID    :: string(),
+         SecKey      :: binary(),
+         RecipientID :: string(),
+         Amount      :: non_neg_integer(),
+         Payload     :: binary(),
+         Result      :: term(), % FIXME
+         Reason      :: chain_error() | string().
+%% @doc
+%% Forms a spend transaction and submits it to the chain.
+
+spend(SenderID, SecKey, RecipientID, Amount, Payload) ->
     case status() of
         {ok, #{"top_block_height" := Height, "network_id" := NetworkID}} ->
-            spend(SenderID, SecKey, ReceipientID, Amount, Payload, Height, NetworkID);
+            spend(SenderID, SecKey, RecipientID, Amount, Payload, Height, NetworkID);
         Error  ->
             Error
     end.
@@ -1699,6 +1728,22 @@ spend(SenderID, SecKey, RecipientID, Amount, Payload, Height, NetworkID) ->
     end.
 
 
+-spec spend(SenderID, SecKey, RecipientID, Amount,
+            GasPrice, Gas, TTL, Nonce, Payload, NetworkID) -> {ok, Result} | {error, Reason}
+    when SenderID    :: string(),
+         SecKey      :: binary(),
+         RecipientID :: string(),
+         Amount      :: non_neg_integer(),
+         GasPrice    :: pos_integer(),
+         Gas         :: pos_integer(),
+         TTL         :: non_neg_integer(),
+         Nonce       :: non_neg_integer(),
+         Payload     :: binary(),
+         Result      :: term(), % FIXME
+         Reason      :: chain_error() | string().
+%% @doc
+%% Forms a spend transaction and submits it to the chain.
+
 spend(SenderID,
       SecKey,
       RecipientID,
@@ -1811,6 +1856,10 @@ spend3(DSenderID,
     when Message :: binary(),
          SecKey  :: binary(),
          Sig     :: binary().
+%% @doc
+%% Accepts a string to be signed, prepends the prefix `"Gajumaru Signed Message:\n"',
+%% encodes the string with `vencode/1', then hashes the encoded message and signs the
+%% hash.
 
 sign_message(Message, SecKey) ->
     Prefix = message_sig_prefix(),
@@ -1889,6 +1938,12 @@ eu(N, Size) ->
     when Binary :: binary(),
          SecKey :: binary(),
          Sig    :: binary().
+%% @doc
+%% This procedure signs an arbitrary binary blob with a special binary prefix
+%% attached. The reason for the binary prefix is to prevent signing of dangerous
+%% binaries which could be used to authorized dangerous actions on chain.
+%% The signature target becomes: `<<"Gajumaru Signed Binary:", Binary/binary>>'
+%% before being hashed, and then the resulting hash is signed.
 
 sign_binary(Binary, SecKey) ->
     Prefix = binary_sig_prefix(),
@@ -1903,6 +1958,8 @@ sign_binary(Binary, SecKey) ->
          PubKey  :: pubkey(),
          Result  :: {ok, Outcome :: boolean()}
                   | {error, Reason :: term()}.
+%% @doc
+%% Verifies a signature created with the `sign_binary/2' function.
 
 verify_bin_signature(Sig, Binary, PubKey) ->
     case gmser_api_encoder:decode(PubKey) of
diff --git a/src/hz_fetcher.erl b/src/hz_fetcher.erl
index 0cf8414..37f931e 100644
--- a/src/hz_fetcher.erl
+++ b/src/hz_fetcher.erl
@@ -1,3 +1,11 @@
+%%% @private
+%%% Hakuzaru Request Fetcher
+%%%
+%%% This module defines the request workers.
+%%% Each request to a remote chain node is handled by a worker that is spawned
+%%% to handle it and terminates on completion.
+%%% @end
+
 -module(hz_fetcher).
 -vsn("0.9.1").
 -author("Craig Everett <ceverett@tsuriai.jp>").