diff --git a/Cargo.lock b/Cargo.lock
index a33cd951311ed..ed449e04457a8 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -513,6 +513,11 @@ name = "difference"
 version = "1.0.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 
+[[package]]
+name = "difference"
+version = "2.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "digest"
 version = "0.7.4"
@@ -1785,6 +1790,15 @@ dependencies = [
  "difference 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "pretty_assertions"
+version = "0.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+dependencies = [
+ "ansi_term 0.11.0 (registry+https://github.com/rust-lang/crates.io-index)",
+ "difference 2.0.0 (registry+https://github.com/rust-lang/crates.io-index)",
+]
+
 [[package]]
 name = "proc-macro-hack"
 version = "0.4.0"
@@ -1922,7 +1936,7 @@ dependencies = [
  "lazy_static 1.0.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "libc 0.2.41 (registry+https://github.com/rust-lang/crates.io-index)",
  "num_cpus 1.8.0 (registry+https://github.com/rust-lang/crates.io-index)",
- "rand 0.3.22 (registry+https://github.com/rust-lang/crates.io-index)",
+ "rand 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
 [[package]]
@@ -2884,8 +2898,10 @@ version = "0.1.0"
 dependencies = [
  "ed25519 0.1.0",
  "hex-literal 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
+ "pretty_assertions 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.70 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_derive 1.0.70 (registry+https://github.com/rust-lang/crates.io-index)",
+ "serde_json 1.0.22 (registry+https://github.com/rust-lang/crates.io-index)",
  "substrate-codec 0.1.0",
  "substrate-primitives 0.1.0",
  "substrate-runtime-io 0.1.0",
@@ -3771,6 +3787,7 @@ dependencies = [
 "checksum ctrlc 1.1.1 (git+https://github.com/paritytech/rust-ctrlc.git)" = "<none>"
 "checksum datastore 0.1.0 (git+https://github.com/tomaka/libp2p-rs?rev=6aa139a12dbea3d75d898ce0b2af7fcec129e294)" = "<none>"
 "checksum difference 1.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "b3304d19798a8e067e48d8e69b2c37f0b5e9b4e462504ad9e27e9f3fce02bba8"
+"checksum difference 2.0.0 (registry+https://github.com/rust-lang/crates.io-index)" = "524cbf6897b527295dff137cec09ecf3a05f4fddffd7dfcd1585403449e74198"
 "checksum digest 0.7.4 (registry+https://github.com/rust-lang/crates.io-index)" = "3cae2388d706b52f2f2f9afe280f9d768be36544bd71d1b8120cb34ea6450b55"
 "checksum dtoa 0.4.2 (registry+https://github.com/rust-lang/crates.io-index)" = "09c3753c3db574d215cba4ea76018483895d7bff25a31b49ba45db21c48e50ab"
 "checksum edit-distance 2.0.1 (registry+https://github.com/rust-lang/crates.io-index)" = "3bd26878c3d921f89797a4e1a1711919f999a9f6946bb6f5a4ffda126d297b7e"
@@ -3897,6 +3914,7 @@ dependencies = [
 "checksum pkg-config 0.3.11 (registry+https://github.com/rust-lang/crates.io-index)" = "110d5ee3593dbb73f56294327fe5668bcc997897097cbc76b51e7aed3f52452f"
 "checksum plain_hasher 0.2.0 (git+https://github.com/paritytech/parity-common)" = "<none>"
 "checksum pretty_assertions 0.4.1 (registry+https://github.com/rust-lang/crates.io-index)" = "28ea5118e2f41bfbc974b28d88c07621befd1fa5d6ec23549be96302a1a59dd2"
+"checksum pretty_assertions 0.5.1 (registry+https://github.com/rust-lang/crates.io-index)" = "3a029430f0d744bc3d15dd474d591bed2402b645d024583082b9f63bb936dac6"
 "checksum proc-macro-hack 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "3ba8d4f9257b85eb6cdf13f055cea3190520aab1409ca2ab43493ea4820c25f0"
 "checksum proc-macro-hack-impl 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)" = "d5cb6f960ad471404618e9817c0e5d10b1ae74cfdf01fab89ea0641fe7fb2892"
 "checksum proc-macro2 0.4.4 (registry+https://github.com/rust-lang/crates.io-index)" = "1fa93823f53cfd0f5ac117b189aed6cfdfb2cfc0a9d82e956dd7927595ed7d46"
diff --git a/substrate/runtime-support/Cargo.toml b/substrate/runtime-support/Cargo.toml
index bef5065ef0f4a..d0c21056af722 100644
--- a/substrate/runtime-support/Cargo.toml
+++ b/substrate/runtime-support/Cargo.toml
@@ -13,6 +13,10 @@ substrate-runtime-io = { path = "../runtime-io", default_features = false }
 substrate-primitives = { path = "../primitives", default_features = false }
 substrate-codec = { path = "../codec", default_features = false }
 
+[dev-dependencies]
+pretty_assertions = "0.5.1"
+serde_json = { version = "1.0" }
+
 [features]
 default = ["std"]
 std = [
diff --git a/substrate/runtime-support/src/dispatch.rs b/substrate/runtime-support/src/dispatch.rs
index 62e34ecb09ca7..7ef9c7cf1c019 100644
--- a/substrate/runtime-support/src/dispatch.rs
+++ b/substrate/runtime-support/src/dispatch.rs
@@ -105,6 +105,11 @@ macro_rules! decl_module {
 			impl for $mod_type<$trait_instance: $trait_name>;
 			$($rest)*
 		}
+
+		__impl_json_metadata! {
+			impl for $mod_type<$trait_instance: $trait_name>;
+			$($rest)*
+		}
 	};
 	(
 		$(#[$attr:meta])*
@@ -128,6 +133,11 @@ macro_rules! decl_module {
 			impl for $mod_type<$trait_instance: $trait_name>;
 			$($rest)*
 		}
+
+		__impl_json_metadata! {
+			impl for $mod_type<$trait_instance: $trait_name>;
+			$($rest)*
+		}
 	}
 }
 
@@ -558,3 +568,241 @@ macro_rules! impl_outer_dispatch_common {
 
 	}
 }
+
+/// Implement the `json_metadata` function.
+#[macro_export]
+macro_rules! __impl_json_metadata {
+	(
+		impl for $mod_type:ident<$trait_instance:ident: $trait_name:ident>;
+		$($rest:tt)*
+	) => {
+		impl<$trait_instance: $trait_name> $mod_type<$trait_instance> {
+			pub fn json_metadata() -> &'static str {
+			    concat!(r#"{ "name": ""#, stringify!($mod_type), r#"", "calls": ["#,
+				    __calls_to_json!(""; $($rest)*), " ] }")
+			}
+		}
+	}
+}
+
+/// Convert the list of calls into their JSON representation, joined by ",".
+#[macro_export]
+macro_rules! __calls_to_json {
+    // WITHOUT AUX
+	(
+		$prefix_str:tt;
+		$(#[$attr:meta])*
+		pub enum $call_type:ident {
+			$(
+				fn $fn_name:ident(
+					$(
+						$param_name:ident : $param:ty
+					),*
+				) -> $result:ty
+				= $id:expr ;
+			)*
+		}
+		$($rest:tt)*
+	) => {
+		concat!($prefix_str, " ",
+		    r#"{ "name": ""#, stringify!($call_type),
+			r#"", "functions": {"#,
+			__functions_to_json!(""; $(
+				fn $fn_name( $( $param_name: $param ),* ) -> $result = $id;
+			)*), " } }", __calls_to_json!(","; $($rest)*)
+		)
+	};
+	// WITH AUX
+	(
+		$prefix_str:tt;
+		$(#[$attr:meta])*
+		pub enum $call_type:ident where aux: $aux_type:ty {
+			$(
+				fn $fn_name:ident(aux
+					$(
+						, $param_name:ident : $param:ty
+					)*
+				) -> $result:ty
+				= $id:expr ;
+			)*
+		}
+		$($rest:tt)*
+	) => {
+		concat!($prefix_str, " ",
+		    r#"{ "name": ""#, stringify!($call_type),
+			r#"", "functions": {"#,
+			__functions_to_json!(""; $aux_type; $(
+				fn $fn_name(aux $(, $param_name: $param )* ) -> $result = $id;
+			)*), " } }", __calls_to_json!(","; $($rest)*)
+		)
+	};
+	// BASE CASE
+	(
+		$prefix_str:tt;
+	) => {
+		""
+	}
+}
+
+/// Convert a list of function into their JSON representation, joined by ",".
+#[macro_export]
+macro_rules! __functions_to_json {
+	// WITHOUT AUX
+    (
+		$prefix_str:tt;
+	    fn $fn_name:ident(
+			$($param_name:ident : $param:ty),*
+		) -> $result:ty = $id:expr ;
+		$($rest:tt)*
+	) => {
+		    concat!($prefix_str, " ",
+				__function_to_json!(
+					fn $fn_name(
+						$($param_name : $param),*
+					) -> $result = $id ;
+				), __functions_to_json!(","; $($rest)*)
+		    )
+	};
+	// WITH AUX
+	(
+		$prefix_str:tt;
+		$aux_type:ty;
+		fn $fn_name:ident(aux
+			$(
+				, $param_name:ident : $param:ty
+			)*
+		) -> $result:ty = $id:expr ;
+		$($rest:tt)*
+	) => {
+			concat!($prefix_str, " ",
+				__function_to_json!(
+					fn $fn_name(
+						aux: $aux_type
+						$(, $param_name : $param)*
+					) -> $result = $id ;
+				), __functions_to_json!(","; $aux_type; $($rest)*)
+		    )
+	};
+	// BASE CASE
+	(
+		$prefix_str:tt;
+		$($aux_type:ty;)*
+	) => {
+		""
+	}
+}
+
+/// Convert a function into its JSON representation.
+#[macro_export]
+macro_rules! __function_to_json {
+    (
+	    fn $fn_name:ident(
+			$first_param_name:ident : $first_param:ty $(, $param_name:ident : $param:ty)*
+		) -> $result:ty = $id:expr ;
+	) => {
+			concat!(
+				r#"""#, stringify!($id), r#"""#,
+				r#": { "name": ""#, stringify!($fn_name),
+				r#"", "params": [ "#,
+				concat!(r#"{ "name": ""#, stringify!($first_param_name), r#"", "type": ""#, stringify!($first_param), r#"" }"# ),
+				$(
+					concat!(r#", { "name": ""#, stringify!($param_name), r#"", "type": ""#, stringify!($param), r#"" }"# ),
+				)*
+				" ] }"
+			)
+	};
+}
+
+#[cfg(test)]
+// Do not complain about unused `dispatch` and `dispatch_aux`.
+#[allow(dead_code)]
+mod tests {
+	use super::*;
+	use serde;
+	use serde_json;
+
+	pub trait Trait {
+		 type PublicAux;
+	}
+
+	decl_module! {
+		pub struct Module<T: Trait>;
+
+		#[derive(Serialize, Deserialize)]
+		pub enum Call where aux: T::PublicAux {
+			fn aux_0(aux) -> Result = 0;
+			fn aux_1(aux, data: i32) -> Result = 1;
+			fn aux_2(aux, data: i32, data2: String) -> Result = 2;
+		}
+
+		#[derive(Serialize, Deserialize)]
+		pub enum PrivCall {
+			 fn priv_0(data: String) -> Result = 0;
+			 fn priv_1(data: String, data2: u32) -> Result = 1;
+		}
+	}
+
+	const EXPECTED_METADATA: &str = concat!(
+		r#"{ "name": "Module", "calls": [ "#,
+			r#"{ "name": "Call", "functions": { "#,
+				r#""0": { "name": "aux_0", "params": [ "#,
+					r#"{ "name": "aux", "type": "T::PublicAux" }"#,
+				r#" ] }, "#,
+				r#""1": { "name": "aux_1", "params": [ "#,
+					r#"{ "name": "aux", "type": "T::PublicAux" }, "#,
+					r#"{ "name": "data", "type": "i32" }"#,
+				r#" ] }, "#,
+				r#""2": { "name": "aux_2", "params": [ "#,
+					r#"{ "name": "aux", "type": "T::PublicAux" }, "#,
+					r#"{ "name": "data", "type": "i32" }, "#,
+					r#"{ "name": "data2", "type": "String" }"#,
+				r#" ] }"#,
+			r#" } }, "#,
+			r#"{ "name": "PrivCall", "functions": { "#,
+				r#""0": { "name": "priv_0", "params": [ "#,
+					r#"{ "name": "data", "type": "String" }"#,
+				r#" ] }, "#,
+				r#""1": { "name": "priv_1", "params": [ "#,
+					r#"{ "name": "data", "type": "String" }, "#,
+					r#"{ "name": "data2", "type": "u32" }"#,
+				r#" ] }"#,
+			r#" } }"#,
+		r#" ] }"#,
+	);
+
+	impl<T: Trait> Module<T> {
+		fn aux_0(_: &T::PublicAux) -> Result {
+			unreachable!()
+		}
+
+		fn aux_1(_: &T::PublicAux, _: i32) -> Result {
+			unreachable!()
+		}
+
+		fn aux_2(_: &T::PublicAux, _: i32, _: String) -> Result {
+			unreachable!()
+		}
+
+		fn priv_0(_: String) -> Result {
+			unreachable!()
+		}
+
+		fn priv_1(_: String, _: u32) -> Result {
+			unreachable!()
+		}
+	}
+
+	struct TraitImpl {}
+
+	impl Trait for TraitImpl {
+		type PublicAux = u32;
+	}
+
+	#[test]
+	fn module_json_metadata() {
+		let metadata = Module::<TraitImpl>::json_metadata();
+		assert_eq!(EXPECTED_METADATA, metadata);
+		let _: serde::de::IgnoredAny =
+			serde_json::from_str(metadata).expect("Is valid json syntax");
+	}
+}
\ No newline at end of file
diff --git a/substrate/runtime-support/src/lib.rs b/substrate/runtime-support/src/lib.rs
index d1ccdc7d397f4..ed22c6413e90d 100644
--- a/substrate/runtime-support/src/lib.rs
+++ b/substrate/runtime-support/src/lib.rs
@@ -25,6 +25,15 @@ extern crate substrate_runtime_std as rstd;
 extern crate substrate_runtime_io as runtime_io;
 extern crate substrate_primitives as primitives;
 
+#[cfg(test)]
+#[macro_use]
+extern crate pretty_assertions;
+#[cfg(test)]
+#[macro_use]
+extern crate serde_derive;
+#[cfg(test)]
+extern crate serde_json;
+
 #[doc(hidden)]
 pub extern crate substrate_codec as codec;
 pub use self::storage::generator::Storage as GenericStorage;