Clarification for the _data parameter

EIPS/eip-1155.md

@@ -91,7 +91,7 @@ interface ERC1155 /* is ERC165 */ {
         @param _to      Target address
         @param _id      ID of the token type
         @param _value   Transfer amount
-        @param _data    Additional data with no specified format, sent in call to `onERC1155Received` on `_to`
+        @param _data    Additional data with no specified format, MUST be sent in call to `onERC1155Received` on `_to`
     */
     function safeTransferFrom(address _from, address _to, uint256 _id, uint256 _value, bytes calldata _data) external;
 
@@ -110,7 +110,7 @@ interface ERC1155 /* is ERC165 */ {
         @param _to      Target addresses
         @param _ids     IDs of each token type (order and length must match _values array)
         @param _values  Transfer amounts per token type (order and length must match _ids array)
-        @param _data    Additional data with no specified format, sent in call to the ERC1155TokenReceiver hook(s) on `_to`
+        @param _data    Additional data with no specified format, MUST be sent in call to the ERC1155TokenReceiver hook(s) on `_to`
     */
     function safeBatchTransferFrom(address _from, address _to, uint256[] calldata _ids, uint256[] calldata _values, bytes calldata _data) external;
 
@@ -274,7 +274,7 @@ To be more explicit about how safeTransferFrom and safeBatchTransferFrom MUST op
     - `_from` MUST be 0x0 for a mint.
 * The `_id` argument MUST be the token type being transferred.
 * The `_value` argument MUST be the number of tokens the holder balance is decreased by and match what the recipient balance is increased by.
-* The `_data` argument MAY contain the extra information provided by the sender for a transfer.
+* The `_data` argument MUST contain the extra information provided by the sender for the transfer.
 * The recipient contract MAY accept an increase of its balance by returning the acceptance magic value `bytes4(keccak256("accept_erc1155_tokens()"))`
     - If the return value is `bytes4(keccak256("accept_erc1155_tokens()"))` the transfer MUST be completed or MUST revert if any other conditions are not met for success.
 * The recipient contract MAY reject an increase of its balance by returning the rejection magic value `bytes4(keccack256("reject_erc1155_tokens()"))`.
@@ -290,7 +290,7 @@ To be more explicit about how safeTransferFrom and safeBatchTransferFrom MUST op
     - `_from` MUST be 0x0 for a mint.    
 * The `_ids` argument MUST be the list of tokens being transferred.
 * The `_values` argument MUST be the list of number of tokens (matching the list and order of tokens specified in `_ids`) the holder balance is decreased by and match what the recipient balance is increased by.
-* The `_data` argument MAY contain the extra information provided by the sender for a transfer.
+* The `_data` argument MUST contain the information provided by the sender for a transfer.
 * The recipient contract MAY accept an increase of its balance by returning the acceptance magic value `bytes4(keccak256("accept_batch_erc1155_tokens()"))`
     - If the return value is `bytes4(keccak256("accept_batch_erc1155_tokens()"))` the transfer MUST be completed or MUST revert if any other conditions are not met for success.
 * The recipient contract MAY reject an increase of its balance by returning the rejection magic value `bytes4(keccack256("reject_erc1155_tokens()"))`.