diff --git a/lib/tt_eth/behaviours/chain_client.ex b/lib/tt_eth/behaviours/chain_client.ex
index 939f452..7e27f04 100644
--- a/lib/tt_eth/behaviours/chain_client.ex
+++ b/lib/tt_eth/behaviours/chain_client.ex
@@ -16,6 +16,7 @@ defmodule TTEth.Behaviours.ChainClient do
   @type filter_params :: map
   @type filter_id :: String.t()
   @type tx_obj :: map()
+  @type error :: {:error, map() | binary() | atom()}
 
   @callback eth_call(contract :: address, encoded_args) :: any
   @callback eth_call(contract :: address, encoded_args, opts) :: any
@@ -26,8 +27,13 @@ defmodule TTEth.Behaviours.ChainClient do
   @callback build_tx_data(address, abi_data, wallet, nonce) :: tx_data
   @callback build_tx_data(address, abi_data, wallet, nonce, keyword) :: tx_data
 
-  @callback eth_get_transaction_count(account :: address, block_id) :: any
-  @callback eth_get_transaction_count(account :: address, block_id, opts) :: any
+  @callback eth_get_balance(account :: address, block_id) :: {:ok, binary()} | error
+  @callback eth_get_balance(account :: address, block_id, opts) :: {:ok, binary()} | error
+
+  @callback eth_get_transaction_count(account :: address, block_id) ::
+              {:ok, binary()} | error
+  @callback eth_get_transaction_count(account :: address, block_id, opts) ::
+              {:ok, binary()} | error
 
   @callback eth_get_logs(filter_params) :: {:ok, any} | {:error, any}
   @callback eth_get_logs(filter_params, opts) :: {:ok, any} | {:error, any}
@@ -47,6 +53,20 @@ defmodule TTEth.Behaviours.ChainClient do
   @callback eth_estimate_gas(tx_obj) :: any
   @callback eth_estimate_gas(tx_obj, opts) :: any
 
+  @callback eth_fee_history(
+              block_count :: integer(),
+              newest_block :: binary(),
+              reward_percentiles :: list(binary())
+            ) ::
+              {:ok, map()} | error
+  @callback eth_fee_history(
+              block_count :: integer(),
+              newest_block :: binary(),
+              reward_percentiles :: list(binary()),
+              opts
+            ) ::
+              {:ok, map()} | error
+
   @callback eth_get_block_by_number(block_id) :: any
   @callback eth_get_block_by_number(block_id, boolean) :: any
 end
diff --git a/lib/tt_eth/chain_client.ex b/lib/tt_eth/chain_client.ex
index c41a3f8..722c3ca 100644
--- a/lib/tt_eth/chain_client.ex
+++ b/lib/tt_eth/chain_client.ex
@@ -66,6 +66,10 @@ defmodule TTEth.ChainClient do
   def eth_estimate_gas(%{} = tx_obj, opts \\ []),
     do: tx_obj |> HttpClient.eth_estimate_gas(opts)
 
+  @impl ChainClient
+  def eth_fee_history(block_count, newest_block, reward_percentiles, opts \\ []),
+    do: HttpClient.eth_fee_history(block_count, newest_block, reward_percentiles, opts)
+
   @impl ChainClient
   def eth_get_block_by_number("" <> block, tx_detail \\ false),
     do: block |> HttpClient.eth_get_block_by_number(tx_detail)
diff --git a/lib/tt_eth/chain_client_mock_impl.ex b/lib/tt_eth/chain_client_mock_impl.ex
index 1430445..d3e1cd2 100644
--- a/lib/tt_eth/chain_client_mock_impl.ex
+++ b/lib/tt_eth/chain_client_mock_impl.ex
@@ -51,6 +51,41 @@ defmodule TTEth.ChainClientMockImpl do
   def eth_estimate_gas(%{} = _tx_obj, _opts \\ []),
     do: {:ok, "0x5208"}
 
+  @impl ChainClient
+  def eth_fee_history(_block_count, _newest_block, _reward_percentiles, _opts \\ []),
+    do:
+      {:ok,
+       [
+         %{
+           "oldestBlock" => "0x54",
+           "reward" => [
+             [
+               "0x174876e800",
+               "0x174876e800"
+             ],
+             [
+               "0x174876e800",
+               "0x174876e800"
+             ],
+             [
+               "0x174876e800",
+               "0x174876e800"
+             ]
+           ],
+           "baseFeePerGas" => [
+             "0x0",
+             "0x0",
+             "0x0",
+             "0x0"
+           ],
+           "gasUsedRatio" => [
+             0.0010253063265735019,
+             0.006479788956353575,
+             0.00006763590977418037
+           ]
+         }
+       ]}
+
   @impl ChainClient
   def eth_get_block_by_number(_block, _tx_detail \\ false),
     do: {:ok, %{"number" => "0x1", "baseFeePerGas" => "0x10"}}