diff --git a/rust/catalyst-signed-doc-macro/src/rules/doc_ref.rs b/rust/catalyst-signed-doc-macro/src/rules/doc_ref.rs
new file mode 100644
index 0000000000..8d460e0af6
--- /dev/null
+++ b/rust/catalyst-signed-doc-macro/src/rules/doc_ref.rs
@@ -0,0 +1,38 @@
+//! `RefRule` generation
+
+use proc_macro2::TokenStream;
+use quote::quote;
+
+use crate::signed_doc_spec::{self, IsRequired};
+
+/// Generating `RefRule` instantiation
+pub(crate) fn ref_rule(ref_spec: &signed_doc_spec::doc_ref::Ref) -> anyhow::Result<TokenStream> {
+    let optional = match ref_spec.required {
+        IsRequired::Yes => false,
+        IsRequired::Optional => true,
+        IsRequired::Excluded => {
+            return Ok(quote! {
+                crate::validator::rules::RefRule::NotSpecified
+            });
+        },
+    };
+
+    anyhow::ensure!(!ref_spec.doc_type.is_empty(), "'type' field should exists and has at least one entry for the required 'ref' metadata definition");
+
+    let const_type_name_idents = ref_spec.doc_type.iter().map(|doc_name| {
+        let const_type_name_ident = doc_name.ident();
+        quote! {
+            crate::doc_types::#const_type_name_ident
+        }
+    });
+    let multiple = ref_spec.multiple.ok_or(anyhow::anyhow!(
+        "'multiple' field should exists for the required 'ref' metadata definition"
+    ))?;
+    Ok(quote! {
+        crate::validator::rules::RefRule::Specified {
+            exp_ref_types: vec![ #(#const_type_name_idents,)* ],
+            multiple: #multiple,
+            optional: #optional,
+        }
+    })
+}
diff --git a/rust/catalyst-signed-doc-macro/src/rules/mod.rs b/rust/catalyst-signed-doc-macro/src/rules/mod.rs
index a8f2d619a0..a8fa819ade 100644
--- a/rust/catalyst-signed-doc-macro/src/rules/mod.rs
+++ b/rust/catalyst-signed-doc-macro/src/rules/mod.rs
@@ -1,5 +1,7 @@
 //! `catalyst_signed_documents_rules!` macro implementation
 
+pub(crate) mod doc_ref;
+
 use proc_macro2::TokenStream;
 use quote::quote;
 
@@ -10,9 +12,10 @@ pub(crate) fn catalyst_signed_documents_rules_impl() -> anyhow::Result<TokenStre
     let spec = CatalystSignedDocSpec::load_signed_doc_spec()?;
 
     let mut rules_definitions = Vec::new();
-    for (doc_name, _doc_spec) in spec.docs {
+    for (doc_name, doc_spec) in spec.docs {
         let const_type_name_ident = doc_name.ident();
 
+        let ref_rule = doc_ref::ref_rule(&doc_spec.metadata.doc_ref)?;
         // TODO: implement a proper initialization for all specific validation rules
         let rules = quote! {
             crate::validator::rules::Rules {
@@ -27,7 +30,7 @@ pub(crate) fn catalyst_signed_documents_rules_impl() -> anyhow::Result<TokenStre
                 },
                 content: crate::validator::rules::ContentRule::NotSpecified,
                 parameters: crate::validator::rules::ParametersRule::NotSpecified,
-                doc_ref: crate::validator::rules::RefRule::NotSpecified,
+                doc_ref: #ref_rule,
                 reply: crate::validator::rules::ReplyRule::NotSpecified,
                 section: crate::validator::rules::SectionRule::NotSpecified,
                 kid: crate::validator::rules::SignatureKidRule {
diff --git a/rust/catalyst-signed-doc-macro/src/signed_doc_spec/doc_ref.rs b/rust/catalyst-signed-doc-macro/src/signed_doc_spec/doc_ref.rs
new file mode 100644
index 0000000000..1384ebf1c6
--- /dev/null
+++ b/rust/catalyst-signed-doc-macro/src/signed_doc_spec/doc_ref.rs
@@ -0,0 +1,13 @@
+//! `signed_doc.json` "ref" field JSON definition
+
+use crate::signed_doc_spec::{DocTypes, IsRequired};
+
+/// `signed_doc.json` "ref" field JSON object
+#[derive(serde::Deserialize)]
+#[allow(clippy::missing_docs_in_private_items)]
+pub(crate) struct Ref {
+    pub(crate) required: IsRequired,
+    #[serde(rename = "type")]
+    pub(crate) doc_type: DocTypes,
+    pub(crate) multiple: Option<bool>,
+}
diff --git a/rust/catalyst-signed-doc-macro/src/signed_doc_spec.rs b/rust/catalyst-signed-doc-macro/src/signed_doc_spec/mod.rs
similarity index 51%
rename from rust/catalyst-signed-doc-macro/src/signed_doc_spec.rs
rename to rust/catalyst-signed-doc-macro/src/signed_doc_spec/mod.rs
index 48eadb18a1..a2cba1d84b 100644
--- a/rust/catalyst-signed-doc-macro/src/signed_doc_spec.rs
+++ b/rust/catalyst-signed-doc-macro/src/signed_doc_spec/mod.rs
@@ -1,8 +1,9 @@
 //! Catalyst Signed Document spec type
 
-use std::collections::HashMap;
+pub(crate) mod doc_ref;
+
+use std::{collections::HashMap, ops::Deref};
 
-use anyhow::Context;
 use proc_macro2::Ident;
 use quote::format_ident;
 
@@ -43,15 +44,66 @@ pub(crate) struct DocSpec {
     /// Document type UUID v4 value
     #[serde(rename = "type")]
     pub(crate) doc_type: String,
+
+    /// Document type metadata definitions
+    pub(crate) metadata: Metadata,
+}
+
+/// Document's metadata fields definition
+#[derive(serde::Deserialize)]
+#[allow(clippy::missing_docs_in_private_items)]
+pub(crate) struct Metadata {
+    #[serde(rename = "ref")]
+    pub(crate) doc_ref: doc_ref::Ref,
+}
+
+/// "required" field definition
+#[derive(serde::Deserialize)]
+#[serde(rename_all = "lowercase")]
+#[allow(clippy::missing_docs_in_private_items)]
+pub(crate) enum IsRequired {
+    Yes,
+    Excluded,
+    Optional,
+}
+
+/// A helper type for deserialization "type" metadata field
+pub(crate) struct DocTypes(Vec<DocumentName>);
+
+impl Deref for DocTypes {
+    type Target = Vec<DocumentName>;
+
+    fn deref(&self) -> &Self::Target {
+        &self.0
+    }
+}
+
+impl<'de> serde::Deserialize<'de> for DocTypes {
+    #[allow(clippy::missing_docs_in_private_items)]
+    fn deserialize<D>(deserializer: D) -> Result<Self, D::Error>
+    where D: serde::Deserializer<'de> {
+        #[derive(serde::Deserialize)]
+        #[serde(untagged)]
+        enum SingleOrVec {
+            Single(DocumentName),
+            Multiple(Vec<DocumentName>),
+        }
+        let value = Option::<SingleOrVec>::deserialize(deserializer)?;
+        let result = match value {
+            Some(SingleOrVec::Single(item)) => vec![item],
+            Some(SingleOrVec::Multiple(items)) => items,
+            None => vec![],
+        };
+        Ok(Self(result))
+    }
 }
 
 impl CatalystSignedDocSpec {
     /// Loading a Catalyst Signed Documents spec from the `signed_doc.json`
     // #[allow(dependency_on_unit_never_type_fallback)]
     pub(crate) fn load_signed_doc_spec() -> anyhow::Result<CatalystSignedDocSpec> {
-        let signed_doc_str = include_str!("../../../specs/signed_doc.json");
-        let signed_doc_spec = serde_json::from_str(signed_doc_str)
-            .context("Catalyst Signed Documents spec must be a JSON object")?;
+        let signed_doc_str = include_str!("../../../../specs/signed_doc.json");
+        let signed_doc_spec = serde_json::from_str(signed_doc_str)?;
         Ok(signed_doc_spec)
     }
 }