diff --git a/lib/ch.ex b/lib/ch.ex
index a027102..073c55c 100644
--- a/lib/ch.ex
+++ b/lib/ch.ex
@@ -2,47 +2,83 @@ defmodule Ch do
   @moduledoc "Minimal HTTP ClickHouse client."
   alias Ch.{Connection, Query, Result}
 
+  @type common_option ::
+          {:database, String.t()}
+          | {:username, String.t()}
+          | {:password, String.t()}
+          | {:settings, Keyword.t()}
+          | {:timeout, timeout}
+
+  @type start_option ::
+          common_option
+          | {:scheme, String.t()}
+          | {:hostname, String.t()}
+          | {:port, :inet.port_number()}
+          | {:transport_opts, :gen_tcp.connect_option()}
+          | DBConnection.start_option()
+
   @doc """
   Start the connection process and connect to ClickHouse.
 
   ## Options
 
+    * `:scheme` - HTTP scheme, defaults to `"http"`
     * `:hostname` - server hostname, defaults to `"localhost"`
     * `:port` - HTTP port, defualts to `8123`
-    * `:scheme` - HTTP scheme, defaults to `"http"`
+    * `:transport_opts` - options to be given to the transport being used. See `Mint.HTTP1.connect/4` for more info
     * `:database` - Database, defaults to `"default"`
     * `:username` - Username
     * `:password` - User password
     * `:settings` - Keyword list of ClickHouse settings
     * `:timeout` - HTTP receive timeout in milliseconds
     * `:transport_opts` - options to be given to the transport being used. See `Mint.HTTP1.connect/4` for more info
+    * [`DBConnection.start_option()`](https://hexdocs.pm/db_connection/DBConnection.html#t:start_option/0)
 
   """
+  @spec start_link([start_option]) :: GenServer.on_start()
   def start_link(opts \\ []) do
     DBConnection.start_link(Connection, opts)
   end
 
   @doc """
   Returns a supervisor child specification for a DBConnection pool.
+
+  See `start_link/1` for supported options.
   """
+  @spec child_spec([start_option]) :: :supervisor.child_spec()
   def child_spec(opts) do
     DBConnection.child_spec(Connection, opts)
   end
 
+  @type query_option ::
+          common_option
+          | {:command, Ch.Query.command()}
+          | {:headers, [{String.t(), String.t()}]}
+          | {:format, String.t()}
+          # TODO remove
+          | {:encode, boolean}
+          | {:decode, boolean}
+          | DBConnection.connection_option()
+
   @doc """
   Runs a query and returns the result as `{:ok, %Ch.Result{}}` or
   `{:error, Exception.t()}` if there was a database error.
 
   ## Options
 
-    * `:timeout` - Query request timeout
-    * `:settings` - Keyword list of settings
     * `:database` - Database
     * `:username` - Username
     * `:password` - User password
+    * `:settings` - Keyword list of settings
+    * `:timeout` - Query request timeout
+    * `:command` - Command tag for the query
+    * `:headers` - Custom HTTP headers for the request
+    * `:format` - Custom response format for the request
+    * `:decode` - Whether to automatically decode the response
+    * [`DBConnection.connection_option()`](https://hexdocs.pm/db_connection/DBConnection.html#t:connection_option/0)
 
   """
-  @spec query(DBConnection.conn(), iodata, params, Keyword.t()) ::
+  @spec query(DBConnection.conn(), iodata, params, [query_option]) ::
           {:ok, Result.t()} | {:error, Exception.t()}
         when params: map | [term] | [row :: [term]] | iodata | Enumerable.t()
   def query(conn, statement, params \\ [], opts \\ []) do
@@ -57,7 +93,7 @@ defmodule Ch do
   Runs a query and returns the result or raises `Ch.Error` if
   there was an error. See `query/4`.
   """
-  @spec query!(DBConnection.conn(), iodata, params, Keyword.t()) :: Result.t()
+  @spec query!(DBConnection.conn(), iodata, params, [query_option]) :: Result.t()
         when params: map | [term] | [row :: [term]] | iodata | Enumerable.t()
   def query!(conn, statement, params \\ [], opts \\ []) do
     query = Query.build(statement, opts)
@@ -65,7 +101,7 @@ defmodule Ch do
   end
 
   @doc false
-  @spec stream(DBConnection.t(), iodata, map | [term], Keyword.t()) :: DBConnection.Stream.t()
+  @spec stream(DBConnection.t(), iodata, map | [term], [query_option]) :: DBConnection.Stream.t()
   def stream(conn, statement, params \\ [], opts \\ []) do
     query = Query.build(statement, opts)
     DBConnection.stream(conn, query, params, opts)
diff --git a/lib/ch/connection.ex b/lib/ch/connection.ex
index 70fcaf7..925de87 100644
--- a/lib/ch/connection.ex
+++ b/lib/ch/connection.ex
@@ -10,7 +10,7 @@ defmodule Ch.Connection do
   @typep conn :: HTTP.t()
 
   @impl true
-  @spec connect(Keyword.t()) :: {:ok, conn} | {:error, Error.t() | Mint.Types.error()}
+  @spec connect([Ch.start_option()]) :: {:ok, conn} | {:error, Error.t() | Mint.Types.error()}
   def connect(opts) do
     scheme = String.to_existing_atom(opts[:scheme] || "http")
     address = opts[:hostname] || "localhost"
@@ -171,7 +171,7 @@ defmodule Ch.Connection do
 
   @typep response :: Mint.Types.status() | Mint.Types.headers() | binary
 
-  @spec request(conn, binary, binary, Mint.Types.headers(), iodata, Keyword.t()) ::
+  @spec request(conn, binary, binary, Mint.Types.headers(), iodata, [Ch.query_option()]) ::
           {:ok, conn, [response]}
           | {:error, Error.t(), conn}
           | {:disconnect, Mint.Types.error(), conn}
diff --git a/lib/ch/query.ex b/lib/ch/query.ex
index 2e6888d..ee44b87 100644
--- a/lib/ch/query.ex
+++ b/lib/ch/query.ex
@@ -2,10 +2,10 @@ defmodule Ch.Query do
   @moduledoc "Query struct wrapping the SQL statement."
   defstruct [:statement, :command, :encode, :decode]
 
-  @type t :: %__MODULE__{statement: iodata, command: atom, encode: boolean, decode: boolean}
+  @type t :: %__MODULE__{statement: iodata, command: command, encode: boolean, decode: boolean}
 
   @doc false
-  @spec build(iodata, Keyword.t()) :: t
+  @spec build(iodata, [Ch.query_option()]) :: t
   def build(statement, opts \\ []) do
     command = Keyword.get(opts, :command) || extract_command(statement)
     encode = Keyword.get(opts, :encode, true)
@@ -43,6 +43,13 @@ defmodule Ch.Query do
     {"WATCH", :watch}
   ]
 
+  command_union =
+    statements
+    |> Enum.map(fn {_, command} -> command end)
+    |> Enum.reduce(&{:|, [], [&1, &2]})
+
+  @type command :: unquote(command_union)
+
   defp extract_command(statement)
 
   for {statement, command} <- statements do
@@ -64,13 +71,14 @@ end
 defimpl DBConnection.Query, for: Ch.Query do
   alias Ch.{Query, Result, RowBinary}
 
-  @spec parse(Query.t(), Keyword.t()) :: Query.t()
+  @spec parse(Query.t(), [Ch.query_option()]) :: Query.t()
   def parse(query, _opts), do: query
 
-  @spec describe(Query.t(), Keyword.t()) :: Query.t()
+  @spec describe(Query.t(), [Ch.query_option()]) :: Query.t()
   def describe(query, _opts), do: query
 
-  @spec encode(Query.t(), params, Keyword.t()) :: {query_params, Mint.Types.headers(), body}
+  @spec encode(Query.t(), params, [Ch.query_option()]) ::
+          {query_params, Mint.Types.headers(), body}
         when params: map | [term] | [row :: [term]] | iodata | Enumerable.t(),
              query_params: [{String.t(), String.t()}],
              body: iodata | Enumerable.t()
@@ -120,7 +128,7 @@ defimpl DBConnection.Query, for: Ch.Query do
     |> format_row_binary?()
   end
 
-  @spec decode(Query.t(), [response], Keyword.t()) :: Result.t()
+  @spec decode(Query.t(), [response], [Ch.query_option()]) :: Result.t()
         when response: Mint.Types.status() | Mint.Types.headers() | binary
   def decode(%Query{command: :insert}, responses, _opts) do
     [_status, headers | _data] = responses
diff --git a/lib/ch/result.ex b/lib/ch/result.ex
index ddca4df..848444d 100644
--- a/lib/ch/result.ex
+++ b/lib/ch/result.ex
@@ -14,7 +14,7 @@ defmodule Ch.Result do
   defstruct [:command, :num_rows, :rows, :headers]
 
   @type t :: %__MODULE__{
-          command: atom,
+          command: Ch.Query.command(),
           num_rows: non_neg_integer | nil,
           rows: [[term]] | iodata | nil,
           headers: Mint.Types.headers()