diff --git a/rpc-toolkit-macro-internals/Cargo.toml b/rpc-toolkit-macro-internals/Cargo.toml
index 977fd8c..508a49c 100644
--- a/rpc-toolkit-macro-internals/Cargo.toml
+++ b/rpc-toolkit-macro-internals/Cargo.toml
@@ -5,6 +5,8 @@ name = "rpc-toolkit-macro-internals"
 version = "0.1.0"
 
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
+[features]
+cli-cookies = []
 
 [dependencies]
 proc-macro2 = "1.0.26"
diff --git a/rpc-toolkit-macro-internals/src/command/build.rs b/rpc-toolkit-macro-internals/src/command/build.rs
index 0d0f91f..72c15c3 100644
--- a/rpc-toolkit-macro-internals/src/command/build.rs
+++ b/rpc-toolkit-macro-internals/src/command/build.rs
@@ -225,7 +225,11 @@ fn build_app(name: LitStr, opt: &mut Options, params: &mut [ParamType]) -> Token
                         modifications.extend(quote_spanned! { ty_span =>
                             arg = arg.takes_value(true);
                         });
-                        if p.path.segments.last().unwrap().ident == "Option" {
+                        if let Some(default) = &arg.default {
+                            modifications.extend(quote_spanned! { ty_span =>
+                                arg = arg.default_value(#default);
+                            });
+                        } else if p.path.segments.last().unwrap().ident == "Option" {
                             arg.optional = true;
                             modifications.extend(quote_spanned! { ty_span =>
                                 arg = arg.required(false);
diff --git a/rpc-toolkit-macro-internals/src/command/mod.rs b/rpc-toolkit-macro-internals/src/command/mod.rs
index 3e458ac..9417e6c 100644
--- a/rpc-toolkit-macro-internals/src/command/mod.rs
+++ b/rpc-toolkit-macro-internals/src/command/mod.rs
@@ -81,6 +81,7 @@ pub struct ArgOptions {
     short: Option<LitStr>,
     long: Option<LitStr>,
     parse: Option<Path>,
+    default: Option<LitStr>,
     count: Option<Path>,
     multiple: Option<Path>,
     stdin: Option<Path>,
diff --git a/rpc-toolkit-macro-internals/src/command/parse.rs b/rpc-toolkit-macro-internals/src/command/parse.rs
index 3779101..a5f6f4b 100644
--- a/rpc-toolkit-macro-internals/src/command/parse.rs
+++ b/rpc-toolkit-macro-internals/src/command/parse.rs
@@ -394,6 +394,7 @@ pub fn parse_arg_attr(attr: Attribute, arg: PatType) -> Result<ArgOptions> {
         short: None,
         long: None,
         parse: None,
+        default: None,
         count: None,
         multiple: None,
         stdin: None,
@@ -627,6 +628,28 @@ pub fn parse_arg_attr(attr: Attribute, arg: PatType) -> Result<ArgOptions> {
                     NestedMeta::Meta(Meta::Path(p)) if p.is_ident("long") => {
                         return Err(Error::new(p.span(), "`long` must be assigned to"));
                     }
+                    NestedMeta::Meta(Meta::NameValue(nv)) if nv.path.is_ident("default") => {
+                        if let Lit::Str(default) = nv.lit {
+                            if opt.default.is_some() {
+                                return Err(Error::new(
+                                    default.span(),
+                                    "duplicate argument `default`",
+                                ));
+                            }
+                            opt.default = Some(default);
+                        } else {
+                            return Err(Error::new(nv.lit.span(), "`default` must be a string"));
+                        }
+                    }
+                    NestedMeta::Meta(Meta::List(list)) if list.path.is_ident("default") => {
+                        return Err(Error::new(
+                            list.path.span(),
+                            "`default` does not take any arguments",
+                        ));
+                    }
+                    NestedMeta::Meta(Meta::Path(p)) if p.is_ident("default") => {
+                        return Err(Error::new(p.span(), "`default` must be assigned to"));
+                    }
                     _ => {
                         return Err(Error::new(arg.span(), "unknown argument"));
                     }
diff --git a/rpc-toolkit-macro/Cargo.toml b/rpc-toolkit-macro/Cargo.toml
index 45acc21..e6a759e 100644
--- a/rpc-toolkit-macro/Cargo.toml
+++ b/rpc-toolkit-macro/Cargo.toml
@@ -9,6 +9,9 @@ version = "0.1.0"
 [lib]
 proc-macro = true
 
+[features]
+cli-cookies = ["rpc-toolkit-macro-internals/cli-cookies"]
+
 [dependencies]
 proc-macro2 = "1.0.1"
 rpc-toolkit-macro-internals = { path = "../rpc-toolkit-macro-internals" }
diff --git a/rpc-toolkit/Cargo.toml b/rpc-toolkit/Cargo.toml
index 9ac5c66..0d5bbba 100644
--- a/rpc-toolkit/Cargo.toml
+++ b/rpc-toolkit/Cargo.toml
@@ -8,18 +8,26 @@ version = "0.1.0"
 [features]
 cbor = ["serde_cbor"]
 default = ["cbor"]
+cli-cookies = ["rpc-toolkit-macro/cli-cookies"]
 
 [dependencies]
 clap = "2.33.3"
 futures = "0.3.15"
-hyper = { version="0.14.5", features=["server", "http1", "http2", "tcp", "stream", "client"] }
+hyper = { version = "0.14.5", features = [
+    "server",
+    "http1",
+    "http2",
+    "tcp",
+    "stream",
+    "client",
+] }
 lazy_static = "1.4.0"
-reqwest = { version="0.11.2" }
-rpc-toolkit-macro = { path="../rpc-toolkit-macro" }
-serde = { version="1.0.125", features=["derive"] }
-serde_cbor = { version="0.11.1", optional=true }
+reqwest = { version = "0.11.2" }
+rpc-toolkit-macro = { path = "../rpc-toolkit-macro" }
+serde = { version = "1.0.125", features = ["derive"] }
+serde_cbor = { version = "0.11.1", optional = true }
 serde_json = "1.0.64"
 thiserror = "1.0.24"
-tokio = { version="1.4.0", features=["full"] }
+tokio = { version = "1.4.0", features = ["full"] }
 url = "2.2.1"
-yajrc = { version="*", path="../../yajrc" }
+yajrc = { version = "*", path = "../../yajrc" }
diff --git a/rpc-toolkit/src/cli_helpers.rs b/rpc-toolkit/src/cli_helpers.rs
new file mode 100644
index 0000000..8b13789
--- /dev/null
+++ b/rpc-toolkit/src/cli_helpers.rs
@@ -0,0 +1 @@
+
diff --git a/rpc-toolkit/src/lib.rs b/rpc-toolkit/src/lib.rs
index 894cfad..3b16067 100644
--- a/rpc-toolkit/src/lib.rs
+++ b/rpc-toolkit/src/lib.rs
@@ -44,6 +44,8 @@ pub use {clap, hyper, reqwest, serde, serde_json, tokio, url, yajrc};
 pub use crate::context::Context;
 pub use crate::metadata::Metadata;
 
+#[cfg(feature = "cli-cookies")]
+pub mod cli_helpers;
 pub mod command_helpers;
 mod context;
 mod metadata;