diff --git a/ur-packages/coin-identity/README.md b/ur-packages/coin-identity/README.md
index 64c4add..9e50371 100644
--- a/ur-packages/coin-identity/README.md
+++ b/ur-packages/coin-identity/README.md
@@ -35,8 +35,8 @@ secp256k1=8         ; SECG secp256k1 curve	IESG
 elliptic_curve = P256 / P384 / P521 / X25519 / X448 / Ed25519 / Ed448 / secp256k1
 
 ; Subtypes specific to some coins (e.g. ChainId for EVM chains)
-hex_string = #6.263(bstr) ; byte string is a hexadecimal string no need for decoding
-sub_type_exp = uint32 / str / hex_string
+hex-string = #6.263(bstr) ; IANA tag 263 — bytes read as a hexadecimal string, no decoding
+sub_type_exp = uint32 / str / hex-string
 
 coin-identity = {
     curve: elliptic_curve,
diff --git a/ur-packages/coin-identity/src/CoinIdentity.ts b/ur-packages/coin-identity/src/CoinIdentity.ts
index 78a30e1..11aea4f 100644
--- a/ur-packages/coin-identity/src/CoinIdentity.ts
+++ b/ur-packages/coin-identity/src/CoinIdentity.ts
@@ -69,8 +69,8 @@ const CoinIdentityBase: RegistryItemClass = registryItemFactory({
     elliptic_curve = P256 / P384 / P521 / X25519 / X448 / Ed25519 / Ed448 / secp256k1
   
     ; Subtypes specific to some coins (e.g. ChainId for EVM chains)
-    hex_string = #6.263(bstr) ; byte string is a hexadecimal string no need for decoding
-    sub_type_exp = uint32 / str / hex_string
+    hex-string = #6.263(bstr) ; IANA tag 263 — bytes read as a hexadecimal string, no decoding
+    sub_type_exp = uint32 / str / hex-string
   
     coin-identity = {
         curve: elliptic_curve,
@@ -102,9 +102,9 @@ const CoinIdentityBase: RegistryItemClass = registryItemFactory({
  *
  * elliptic_curve = P256 / P384 / P521 / X25519 / X448 / Ed25519 / Ed448 / secp256k1
  *
- * ; Subtypes specific to some coins (e.g. ChainId for EVM chains)  
- * hex_string = #6.263(bstr) ; byte string is a hexadecimal string no need for decoding  
- * sub_type_exp = uint32 / str / hex_string  
+ * ; Subtypes specific to some coins (e.g. ChainId for EVM chains)
+ * hex-string = #6.263(bstr) ; IANA tag 263 — bytes read as a hexadecimal string, no decoding
+ * sub_type_exp = uint32 / str / hex-string
  *
  * coin-identity = {
  *     curve: elliptic_curve,  
diff --git a/ur-packages/hex-string/src/HexString.ts b/ur-packages/hex-string/src/HexString.ts
index c505074..ae67be2 100644
--- a/ur-packages/hex-string/src/HexString.ts
+++ b/ur-packages/hex-string/src/HexString.ts
@@ -17,8 +17,7 @@ const HexStringBase: RegistryItemClass = registryItemFactory({
   tag: 263,
   URType: 'hex-string',
   CDDL: `
-    hexadecimal-tag = #6.263(hex-bytes)
-    hex-bytes = bytes
+    hex-string = #6.263(bstr)
   `,
 })
 
diff --git a/ur-packages/hex-string/src/addToRegistry.ts b/ur-packages/hex-string/src/addToRegistry.ts
index 6307682..1dab74d 100644
--- a/ur-packages/hex-string/src/addToRegistry.ts
+++ b/ur-packages/hex-string/src/addToRegistry.ts
@@ -1,5 +1,5 @@
 import { UrRegistry } from '@ngraveio/bc-ur'
 import { HexString } from './HexString'
 
-// Add hexstring to the global registry
+// Add hex-string to the global registry
 UrRegistry.addItemOnce(HexString);
\ No newline at end of file
diff --git a/ur-packages/multi-layer-sync/README.md b/ur-packages/multi-layer-sync/README.md
index e8e5bfb..91e84a9 100644
--- a/ur-packages/multi-layer-sync/README.md
+++ b/ur-packages/multi-layer-sync/README.md
@@ -76,6 +76,8 @@ import { DetailedAccount, PortfolioCoin, PortfolioMetadata, Portfolio } from '@n
 
 The `DetailedAccount` class represents an account with detailed information, including the HDKey and optional token IDs.
 
+Token IDs that are canonically hexadecimal (e.g. EVM ERC20 contract addresses) are encoded using [CBOR tag 263 (hex-string)](https://github.com/toravir/CBOR-Tag-Specs/blob/master/hexString.md) to halve the on-wire size versus the equivalent `0x…` text. All other identifiers — including compound ids for ERC721/ERC1155 and SPL mint addresses — are encoded as plain text strings (`tstr`), following the UAI `tokenid[.subtype…]` convention from [NBCR-2024-001](https://github.com/ngraveio/Research/blob/main/papers/nbcr-2024-001-unique-asset-id.md).
+
 ```mermaid
 flowchart TB
     subgraph DetailedAccount
@@ -88,30 +90,34 @@ flowchart TB
 **CDDL Definition:**
 ```CDDL
 account_exp = #6.40303(hdkey) / #6.40308(output-descriptor)
+hex-string = #6.263(bstr)
 
-; Accounts are specified using either '#6.40303(hdkey)' or 
+; Accounts are specified using either '#6.40303(hdkey)' or
 ; '#6.40308(output-descriptor)'.
 ; By default, '#6.40303(hdkey)' should be used to share public keys and
 ; extended public keys.
-; '#6.308(output-descriptor)' should be used to share an output descriptor, 
+; '#6.40308(output-descriptor)' should be used to share an output descriptor,
 ; e.g. for the different Bitcoin address formats (P2PKH, P2SH-P2WPKH, P2WPKH, P2TR).
+;
+; 'hex-string' (IANA tag 263) wraps bytes meant to be read as a hexadecimal
+; string — the tag preserves hex semantics for display and comparison.
 
 ; Optional 'token-ids' to indicate the synchronization of a list of tokens with
-; the associated accounts
-; 'token-id' is defined differently depending on the blockchain:
-; - ERC20 tokens on EVM chains are identified by their contract addresses 
-; (e.g. `0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48`)
-; - ERC1155 tokens are identifed with their contract addresses followed by their 
-; ID with ':' as separator (e.g. `0xfaafdc07907ff5120a76b34b731b278c38d6043c:
-; 508851954656174721695133294256171964208`)
-; - ESDT tokens on MultiversX are by their name followed by their ID with `-` as 
-; separator (e.g. `USDC-c76f1f`)
-; - SPL tokens on Solana are identified by their contract addresses
-; (e.g. `EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v`)
-
-detailed-account = { 
+; the associated accounts.
+; 'token-id' encoding follows the Unique Asset Identifier (UAI) convention —
+; see NBCR-2024-001. A token-id is either a scalar identifier or a compound
+; "parent.subtype[.subtype...]" form. Current encodings per blockchain:
+; - ERC20 tokens on EVM chains are identified by their contract addresses,
+;   encoded as 'hex-string' (e.g. `0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48`).
+; - ERC721 / ERC1155 tokens are identified by contract address plus token id,
+;   encoded as tstr using the UAI "contract.tokenId" form (e.g.
+;   `0xfaafdc07907ff5120a76b34b731b278c38d6043c.508851954656174721695133294256171964208`).
+; - SPL / Token-2022 on Solana are identified by their mint address,
+;   encoded as tstr (e.g. `EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v`).
+
+detailed-account = {
   account: account_exp,
-  ? token-ids: [+ string / bytes] ; Specify multiple tokens associated to one account
+  ? token-ids: [+ tstr / hex-string] ; Specify multiple tokens associated to one account
 }
 
 account = 1
diff --git a/ur-packages/multi-layer-sync/src/DetailedAccount.ts b/ur-packages/multi-layer-sync/src/DetailedAccount.ts
index 622a667..2f49ff2 100644
--- a/ur-packages/multi-layer-sync/src/DetailedAccount.ts
+++ b/ur-packages/multi-layer-sync/src/DetailedAccount.ts
@@ -19,34 +19,38 @@ export class DetailedAccount extends registryItemFactory({
   allowKeysNotInMap: false,
   CDDL: `
     account_exp = #6.40303(hdkey) / #6.40308(output-descriptor)
+    hex-string = #6.263(bstr)
 
-    ; Accounts are specified using either '#6.40303(hdkey)' or 
+    ; Accounts are specified using either '#6.40303(hdkey)' or
     ; '#6.40308(output-descriptor)'.
     ; By default, '#6.40303(hdkey)' should be used to share public keys and
     ; extended public keys.
-    ; '#6.308(output-descriptor)' should be used to share an output descriptor, 
+    ; '#6.40308(output-descriptor)' should be used to share an output descriptor,
     ; e.g. for the different Bitcoin address formats (P2PKH, P2SH-P2WPKH, P2WPKH, P2TR).
+    ;
+    ; 'hex-string' (IANA tag 263) wraps bytes meant to be read as a hexadecimal
+    ; string — the tag preserves hex semantics for display and comparison.
 
     ; Optional 'token-ids' to indicate the synchronization of a list of tokens with
-    ; the associated accounts
-    ; 'token-id' is defined differently depending on the blockchain:
-    ; - ERC20 tokens on EVM chains are identified by their contract addresses 
-    ; (e.g. "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48")
-    ; - ERC1155 tokens are identifed with their contract addresses followed by their 
-    ; ID with ':' as separator (e.g. "0xfaafdc07907ff5120a76b34b731b278c38d6043c:
-    ; 508851954656174721695133294256171964208")
-    ; - ESDT tokens on MultiversX are by their name followed by their ID with "-" as 
-    ; separator (e.g. "USDC-c76f1f")
-    ; - SPL tokens on Solana are identified by their contract addresses
-    ; (e.g. "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v")
-
-    detailed-account = { 
+    ; the associated accounts.
+    ; 'token-id' encoding follows the Unique Asset Identifier (UAI) convention —
+    ; see NBCR-2024-001. A token-id is either a scalar identifier or a compound
+    ; "parent.subtype[.subtype...]" form. Current encodings per blockchain:
+    ; - ERC20 tokens on EVM chains are identified by their contract addresses,
+    ;   encoded as 'hex-string' (e.g. "0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48").
+    ; - ERC721 / ERC1155 tokens are identified by contract address plus token id,
+    ;   encoded as tstr using the UAI "contract.tokenId" form (e.g.
+    ;   "0xfaafdc07907ff5120a76b34b731b278c38d6043c.508851954656174721695133294256171964208").
+    ; - SPL / Token-2022 on Solana are identified by their mint address,
+    ;   encoded as tstr (e.g. "EPjFWdd5AufqSSqeM2qN1xzybapC8G4wEGGkZwyTDt1v").
+
+    detailed-account = {
       account: account_exp,
-      ? token-ids: [+ string / bytes] ; Specify multiple tokens associated to one account
+      ? token-ids: [+ tstr / hex-string] ; Specify multiple tokens associated to one account
     }
 
     account = 1
-    token-ids = 2  
+    token-ids = 2
   `,
 }) {
   data: {
@@ -55,23 +59,19 @@ export class DetailedAccount extends registryItemFactory({
   }
 
   constructor(data: IDetailAccountInput) {
-    // Token Ids are just hex string for erc20 token like 0xA0b86991c6218b36c1d19D4a2e9Eb0cE3606eB48
-    // For ESDT and SPL types its going to be encoded as string
-    // We will try to parse the string into bytes with removing 0x part,
-    // if we cannot we will encode it as utf8 string
+    // Promote hex-shaped inputs to HexString so they serialise as #6.263(bstr);
+    // other strings stay tstr.
     super(data)
     //@ts-ignore
     this.data = data
 
     let tokenIds = data.tokenIds
 
-    // If token ids are provided, convert them to hex strings
     if (tokenIds !== undefined && Array.isArray(data.tokenIds)) {
-      // Try to parse them into hex strings
+      // Try each id as hex; already-HexString passes through, non-hex input
+      // throws and falls back to tstr.
       tokenIds = tokenIds.map(tokenId => {
-        // If its already hexstring, return it
-        if (tokenId instanceof HexString) return tokenId as HexString
-        // If its buffer or a string try to parse as HexString
+        if (tokenId instanceof HexString) return tokenId
         try {
           return new HexString(tokenId)
         } catch (error) {
@@ -126,13 +126,12 @@ export class DetailedAccount extends registryItemFactory({
   public getOutputDescriptor = () => {
     return this.data.account instanceof OutputDescriptor ? this.data.account : undefined
   }
+  /** Hex-encoded token ids are rendered with a `0x` prefix for round-trip parity. */
   public getTokenIds = () => {
     if (!this.data.tokenIds) return undefined
 
-    // Always return string representation of the token ids
     return this.data.tokenIds.map((tokenId: HexString | string) => {
       if (tokenId instanceof HexString) {
-        // Shall we really add 0x to start?
         return '0x' + tokenId.getData()
       }
       return tokenId