diff --git a/frame-metadata/Cargo.toml b/frame-metadata/Cargo.toml
index a4c1f5d..394986c 100644
--- a/frame-metadata/Cargo.toml
+++ b/frame-metadata/Cargo.toml
@@ -25,5 +25,6 @@ v13 = ["scale-info"]
 std = [
 	"codec/std",
 	"scale-info/std",
+	"scale-info/serde",
 	"serde",
 ]
diff --git a/frame-metadata/src/lib.rs b/frame-metadata/src/lib.rs
index 65fe1c5..4aec005 100644
--- a/frame-metadata/src/lib.rs
+++ b/frame-metadata/src/lib.rs
@@ -22,7 +22,10 @@
 cfg_if::cfg_if! {
 	if #[cfg(feature = "std")] {
 		use codec::{Decode, Error, Input};
-		use serde::Serialize;
+		use serde::{
+			Deserialize,
+			Serialize,
+		};
 	} else {
 		extern crate alloc;
 		use alloc::vec::Vec;
@@ -37,14 +40,29 @@ pub mod v12;
 #[cfg(feature = "v13")]
 pub mod v13;
 
+cfg_if::cfg_if! {
+	if #[cfg(not(feature = "v13"))] {
+		/// Dummy trait in place of `scale_info::form::FormString`.
+		/// Since the `scale-info` crate is only imported for the `v13` feature.
+		pub trait FormString {}
+
+		impl FormString for &'static str {}
+		#[cfg(feature = "std")]
+		impl FormString for String {}
+	} else {
+		pub(crate) use scale_info::form::FormString;
+	}
+}
+
 /// The metadata of a runtime.
 /// The version ID encoded/decoded through
 /// the enum nature of `RuntimeMetadata`.
 #[derive(Eq, Encode, PartialEq)]
 #[cfg_attr(feature = "std", derive(Decode, Serialize, Debug))]
-pub enum RuntimeMetadata {
+#[cfg_attr(feature = "std", serde(bound(serialize = "S: Serialize")))]
+pub enum RuntimeMetadata<S: FormString = &'static str> {
 	/// Unused; enum filler.
-	V0(RuntimeMetadataDeprecated),
+	V0(core::marker::PhantomData<S>),
 	/// Version 1 for runtime metadata. No longer used.
 	V1(RuntimeMetadataDeprecated),
 	/// Version 2 for runtime metadata. No longer used.
@@ -69,13 +87,13 @@ pub enum RuntimeMetadata {
 	V11(RuntimeMetadataDeprecated),
 	/// Version 12 for runtime metadata
 	#[cfg(feature = "v12")]
-	V12(v12::RuntimeMetadataV12),
+	V12(v12::RuntimeMetadataV12<S>),
 	/// Version 12 for runtime metadata, as raw encoded bytes.
 	#[cfg(not(feature = "v12"))]
 	V12(OpaqueMetadata),
 	/// Version 13 for runtime metadata.
 	#[cfg(feature = "v13")]
-	V13(v13::RuntimeMetadataV13),
+	V13(v13::RuntimeMetadataV13<S>),
 	/// Version 13 for runtime metadata, as raw encoded bytes.
 	#[cfg(not(feature = "v13"))]
 	V13(OpaqueMetadata),
@@ -83,12 +101,12 @@ pub enum RuntimeMetadata {
 
 /// Stores the encoded `RuntimeMetadata` as raw bytes.
 #[derive(Encode, Eq, PartialEq)]
-#[cfg_attr(feature = "std", derive(Decode, Serialize, Debug))]
+#[cfg_attr(feature = "std", derive(Decode, Serialize, Deserialize, Debug))]
 pub struct OpaqueMetadata(pub Vec<u8>);
 
 /// Enum that should fail.
 #[derive(Eq, PartialEq)]
-#[cfg_attr(feature = "std", derive(Serialize, Debug))]
+#[cfg_attr(feature = "std", derive(Serialize, Deserialize, Debug))]
 pub enum RuntimeMetadataDeprecated {}
 
 impl Encode for RuntimeMetadataDeprecated {
diff --git a/frame-metadata/src/v12.rs b/frame-metadata/src/v12.rs
index 99562de..4b6e0ec 100644
--- a/frame-metadata/src/v12.rs
+++ b/frame-metadata/src/v12.rs
@@ -35,6 +35,9 @@ cfg_if::cfg_if! {
 	}
 }
 
+use super::FormString;
+use core::marker::PhantomData;
+
 /// Current prefix of metadata
 pub const META_RESERVED: u32 = 0x6174656d; // 'meta' warn endianness
 
@@ -347,7 +350,10 @@ pub struct StorageMetadata {
 /// Metadata prefixed by a u32 for reserved usage
 #[derive(Eq, Encode, PartialEq)]
 #[cfg_attr(feature = "std", derive(Decode, Serialize, Debug))]
-pub struct RuntimeMetadataPrefixed(pub u32, pub super::RuntimeMetadata);
+pub struct RuntimeMetadataPrefixed<S: FormString = &'static str>(
+	pub u32,
+	pub super::RuntimeMetadata<S>,
+);
 
 /// Metadata of the extrinsic used by the runtime.
 #[derive(Eq, Encode, PartialEq)]
@@ -362,11 +368,14 @@ pub struct ExtrinsicMetadata {
 /// The metadata of a runtime.
 #[derive(Eq, Encode, PartialEq)]
 #[cfg_attr(feature = "std", derive(Decode, Serialize, Debug))]
-pub struct RuntimeMetadataV12 {
+#[cfg_attr(feature = "std", serde(bound(serialize = "S: Serialize")))]
+pub struct RuntimeMetadataV12<S = ()> {
 	/// Metadata of all the modules.
 	pub modules: DecodeDifferentArray<ModuleMetadata>,
 	/// Metadata of the extrinsic.
 	pub extrinsic: ExtrinsicMetadata,
+	/// Marker for dummy type parameter required by v13 but not used here.
+	pub marker: PhantomData<S>,
 }
 
 /// The latest version of the metadata.
diff --git a/frame-metadata/src/v13.rs b/frame-metadata/src/v13.rs
index b5b744e..f09b6b2 100644
--- a/frame-metadata/src/v13.rs
+++ b/frame-metadata/src/v13.rs
@@ -17,7 +17,7 @@
 
 cfg_if::cfg_if! {
 	if #[cfg(feature = "std")] {
-		use codec::{Decode, Error, Input};
+		use codec::Decode;
 		use serde::Serialize;
 	}
 }
@@ -38,7 +38,11 @@ pub type ByteGetter = Vec<u8>;
 /// Metadata prefixed by a u32 for reserved usage
 #[derive(Eq, Encode, PartialEq)]
 #[cfg_attr(feature = "std", derive(Decode, Serialize, Debug))]
-pub struct RuntimeMetadataPrefixed(pub u32, pub super::RuntimeMetadata);
+#[cfg_attr(feature = "std", serde(bound(serialize = "S: Serialize")))]
+pub struct RuntimeMetadataPrefixed<S: FormString = &'static str>(
+	pub u32,
+	pub super::RuntimeMetadata<S>,
+);
 
 pub type RuntimeMetadataLastVersion = RuntimeMetadataV13;
 
@@ -52,12 +56,13 @@ impl From<RuntimeMetadataLastVersion> for RuntimeMetadataPrefixed {
 // todo: [AJ] add back clone derive if required (requires PortableRegistry to implement clone)
 #[derive(PartialEq, Eq, Encode)]
 #[cfg_attr(feature = "std", derive(Decode, Serialize, Debug))]
+#[cfg_attr(feature = "std", serde(bound(serialize = "S: Serialize")))]
 pub struct RuntimeMetadataV13<S: FormString = &'static str> {
 	pub types: PortableRegistry<S>,
 	/// Metadata of all the modules.
-	pub modules: Vec<ModuleMetadata<PortableForm>>,
+	pub modules: Vec<ModuleMetadata<PortableForm<S>>>,
 	/// Metadata of the extrinsic.
-	pub extrinsic: ExtrinsicMetadata<PortableForm>,
+	pub extrinsic: ExtrinsicMetadata<PortableForm<S>>,
 }
 
 impl RuntimeMetadataV13 {
@@ -74,13 +79,19 @@ impl RuntimeMetadataV13 {
 }
 
 /// Metadata of the extrinsic used by the runtime.
-#[derive(Clone, PartialEq, Eq, Encode, Debug)]
-#[cfg_attr(feature = "std", derive(Decode))]
+#[derive(Clone, PartialEq, Eq, Encode)]
+#[cfg_attr(feature = "std", derive(Decode, Serialize, Debug))]
+#[cfg_attr(
+	feature = "std",
+	serde(bound(serialize = "T::Type: Serialize, T::String: Serialize"))
+)]
 pub struct ExtrinsicMetadata<T: Form = MetaForm> {
+	/// The type of the extrinsic.
+	pub ty: T::Type,
 	/// Extrinsic version.
 	pub version: u8,
 	/// The signed extensions in the order they appear in the extrinsic.
-	pub signed_extensions: Vec<T::Type>,
+	pub signed_extensions: Vec<SignedExtensionMetadata<T>>,
 }
 
 impl IntoPortable for ExtrinsicMetadata {
@@ -88,8 +99,34 @@ impl IntoPortable for ExtrinsicMetadata {
 
 	fn into_portable(self, registry: &mut Registry) -> Self::Output {
 		ExtrinsicMetadata {
+			ty: registry.register_type(&self.ty),
 			version: self.version,
-			signed_extensions: registry.register_types(self.signed_extensions),
+			signed_extensions: registry.map_into_portable(self.signed_extensions),
+		}
+	}
+}
+
+/// Metadata of an extrinsic's signed extension.
+#[derive(Clone, PartialEq, Eq, Encode)]
+#[cfg_attr(feature = "std", derive(Decode, Serialize, Debug))]
+#[cfg_attr(
+	feature = "std",
+	serde(bound(serialize = "T::Type: Serialize, T::String: Serialize"))
+)]
+pub struct SignedExtensionMetadata<T: Form = MetaForm> {
+	/// The unique signed extension identifier, which may be different from the type name.
+	pub identifier: T::String,
+	/// The signed extensions in the order they appear in the extrinsic.
+	pub ty: T::Type,
+}
+
+impl IntoPortable for SignedExtensionMetadata {
+	type Output = SignedExtensionMetadata<PortableForm>;
+
+	fn into_portable(self, registry: &mut Registry) -> Self::Output {
+		SignedExtensionMetadata {
+			identifier: self.identifier.into_portable(registry),
+			ty: registry.register_type(&self.ty),
 		}
 	}
 }
@@ -97,13 +134,20 @@ impl IntoPortable for ExtrinsicMetadata {
 /// All metadata about an runtime module.
 #[derive(Clone, PartialEq, Eq, Encode)]
 #[cfg_attr(feature = "std", derive(Decode, Serialize, Debug))]
+#[cfg_attr(
+	feature = "std",
+	serde(bound(serialize = "T::Type: Serialize, T::String: Serialize"))
+)]
 pub struct ModuleMetadata<T: Form = MetaForm> {
 	pub name: T::String,
 	pub storage: Option<Vec<StorageMetadata<T>>>,
 	pub calls: Option<Vec<FunctionMetadata<T>>>,
 	pub event: Option<Vec<EventMetadata<T>>>,
-	// pub constants: DFnA<ModuleConstantMetadata>,
+	pub constants: Option<Vec<ModuleConstantMetadata<T>>>,
 	pub errors: Vec<ErrorMetadata<T>>,
+	/// Define the index of the module, this index will be used for the encoding of module event,
+	/// call and origin variants.
+	pub index: u8,
 }
 
 impl IntoPortable for ModuleMetadata {
@@ -117,7 +161,11 @@ impl IntoPortable for ModuleMetadata {
 				.map(|storage| registry.map_into_portable(storage)),
 			calls: self.calls.map(|calls| registry.map_into_portable(calls)),
 			event: self.event.map(|event| registry.map_into_portable(event)),
+			constants: self
+				.constants
+				.map(|constant| registry.map_into_portable(constant)),
 			errors: registry.map_into_portable(self.errors),
+			index: self.index,
 		}
 	}
 }
@@ -125,6 +173,10 @@ impl IntoPortable for ModuleMetadata {
 /// All metadata of the storage.
 #[derive(Clone, PartialEq, Eq, Encode)]
 #[cfg_attr(feature = "std", derive(Decode, Serialize, Debug))]
+#[cfg_attr(
+	feature = "std",
+	serde(bound(serialize = "T::Type: Serialize, T::String: Serialize"))
+)]
 pub struct StorageMetadata<T: Form = MetaForm> {
 	/// The common prefix used by all storage entries.
 	pub prefix: T::String,
@@ -145,6 +197,10 @@ impl IntoPortable for StorageMetadata {
 /// All the metadata about one storage entry.
 #[derive(Clone, PartialEq, Eq, Encode)]
 #[cfg_attr(feature = "std", derive(Decode, Serialize, Debug))]
+#[cfg_attr(
+	feature = "std",
+	serde(bound(serialize = "T::Type: Serialize, T::String: Serialize"))
+)]
 pub struct StorageEntryMetadata<T: Form = MetaForm> {
 	pub name: T::String,
 	pub modifier: StorageEntryModifier,
@@ -191,6 +247,10 @@ pub enum StorageHasher {
 /// A storage entry type.
 #[derive(Clone, PartialEq, Eq, Encode)]
 #[cfg_attr(feature = "std", derive(Decode, Serialize, Debug))]
+#[cfg_attr(
+	feature = "std",
+	serde(bound(serialize = "T::Type: Serialize, T::String: Serialize"))
+)]
 pub enum StorageEntryType<T: Form = MetaForm> {
 	Plain(T::String),
 	Map {
@@ -244,8 +304,12 @@ impl IntoPortable for StorageEntryType {
 }
 
 /// All the metadata about a function.
-#[derive(Clone, PartialEq, Eq, Encode, Debug)]
-#[cfg_attr(feature = "std", derive(Decode))]
+#[derive(Clone, PartialEq, Eq, Encode)]
+#[cfg_attr(feature = "std", derive(Decode, Serialize, Debug))]
+#[cfg_attr(
+	feature = "std",
+	serde(bound(serialize = "T::Type: Serialize, T::String: Serialize"))
+)]
 pub struct FunctionMetadata<T: Form = MetaForm> {
 	pub name: T::String,
 	pub arguments: Vec<FunctionArgumentMetadata<T>>,
@@ -265,8 +329,12 @@ impl IntoPortable for FunctionMetadata {
 }
 
 /// All the metadata about a function argument.
-#[derive(Clone, PartialEq, Eq, Encode, Debug)]
-#[cfg_attr(feature = "std", derive(Decode))]
+#[derive(Clone, PartialEq, Eq, Encode)]
+#[cfg_attr(feature = "std", derive(Decode, Serialize, Debug))]
+#[cfg_attr(
+	feature = "std",
+	serde(bound(serialize = "T::Type: Serialize, T::String: Serialize"))
+)]
 pub struct FunctionArgumentMetadata<T: Form = MetaForm> {
 	pub name: T::String,
 	pub ty: T::Type,
@@ -286,8 +354,12 @@ impl IntoPortable for FunctionArgumentMetadata {
 }
 
 /// All the metadata about an outer event.
-#[derive(Clone, PartialEq, Eq, Encode, Debug)]
-#[cfg_attr(feature = "std", derive(Decode))]
+#[derive(Clone, PartialEq, Eq, Encode)]
+#[cfg_attr(feature = "std", derive(Decode, Serialize, Debug))]
+#[cfg_attr(
+	feature = "std",
+	serde(bound(serialize = "T::Type: Serialize, T::String: Serialize"))
+)]
 pub struct OuterEventMetadata<T: Form = MetaForm> {
 	pub name: T::String,
 	pub events: Vec<ModuleEventMetadata<T>>,
@@ -305,8 +377,12 @@ impl IntoPortable for OuterEventMetadata {
 }
 
 /// Metadata about a module event.
-#[derive(Clone, PartialEq, Eq, Encode, Debug)]
-#[cfg_attr(feature = "std", derive(Decode))]
+#[derive(Clone, PartialEq, Eq, Encode)]
+#[cfg_attr(feature = "std", derive(Decode, Serialize, Debug))]
+#[cfg_attr(
+	feature = "std",
+	serde(bound(serialize = "T::Type: Serialize, T::String: Serialize"))
+)]
 pub struct ModuleEventMetadata<T: Form = MetaForm> {
 	pub name: T::String,
 	pub events: Vec<EventMetadata<T>>,
@@ -324,8 +400,12 @@ impl IntoPortable for ModuleEventMetadata {
 }
 
 /// All the metadata about an event.
-#[derive(Clone, PartialEq, Eq, Encode, Debug)]
-#[cfg_attr(feature = "std", derive(Decode))]
+#[derive(Clone, PartialEq, Eq, Encode)]
+#[cfg_attr(feature = "std", derive(Decode, Serialize, Debug))]
+#[cfg_attr(
+	feature = "std",
+	serde(bound(serialize = "T::Type: Serialize, T::String: Serialize"))
+)]
 pub struct EventMetadata<T: Form = MetaForm> {
 	pub name: T::String,
 	pub arguments: Vec<TypeSpec<T>>,
@@ -344,9 +424,40 @@ impl IntoPortable for EventMetadata {
 	}
 }
 
+/// All the metadata about one module constant.
+#[derive(Clone, PartialEq, Eq, Encode)]
+#[cfg_attr(feature = "std", derive(Decode, Serialize, Debug))]
+#[cfg_attr(
+	feature = "std",
+	serde(bound(serialize = "T::Type: Serialize, T::String: Serialize"))
+)]
+pub struct ModuleConstantMetadata<T: Form = MetaForm> {
+	pub name: T::String,
+	pub ty: T::Type,
+	pub value: ByteGetter,
+	pub documentation: Vec<T::String>,
+}
+
+impl IntoPortable for ModuleConstantMetadata {
+	type Output = ModuleConstantMetadata<PortableForm>;
+
+	fn into_portable(self, registry: &mut Registry) -> Self::Output {
+		ModuleConstantMetadata {
+			name: self.name.into_portable(registry),
+			ty: registry.register_type(&self.ty),
+			value: self.value,
+			documentation: registry.map_into_portable(self.documentation),
+		}
+	}
+}
+
 /// All the metadata about a module error.
 #[derive(Clone, PartialEq, Eq, Encode)]
 #[cfg_attr(feature = "std", derive(Decode, Serialize, Debug))]
+#[cfg_attr(
+	feature = "std",
+	serde(bound(serialize = "T::Type: Serialize, T::String: Serialize"))
+)]
 pub struct ErrorMetadata<T: Form = MetaForm> {
 	pub name: T::String,
 	pub documentation: Vec<T::String>,
@@ -380,8 +491,12 @@ impl IntoPortable for ErrorMetadata {
 /// `pred`'s display name is `Predicate` and the display name of
 /// the return type is simply `bool`. Note that `Predicate` could
 /// simply be a type alias to `fn(i32, i32) -> Ordering`.
-#[derive(Clone, PartialEq, Eq, Encode, Debug)]
-#[cfg_attr(feature = "std", derive(Decode))]
+#[derive(Clone, PartialEq, Eq, Encode)]
+#[cfg_attr(feature = "std", derive(Decode, Serialize, Debug))]
+#[cfg_attr(
+	feature = "std",
+	serde(bound(serialize = "T::Type: Serialize, T::String: Serialize"))
+)]
 pub struct TypeSpec<T: Form = MetaForm> {
 	/// The actual type.
 	pub ty: T::Type,