EVM-C: Clarify encoding of error messages
@@ -86,9 +86,12 @@ struct evm_result {
///
/// The output contains data coming from RETURN opcode (iff evm_result::code
/// field is ::EVM_SUCCESS) or from REVERT opcode (iff evm_result::code
- /// field is ::EVM_REVERT). In case the evm_result::code field signals
- /// a failure the output can contain optional explanation of the failure
- /// for debugging or tracing purposes.
+ /// field is ::EVM_REVERT).
+ ///
+ /// In case the evm_result::code field signals
+ /// a failure the output MAY contain optional explanation of the failure
+ /// for debugging or tracing purposes. In case the explanation is provided
+ /// and contains human-readable text the UTF-8 encoding SHOULD be used.
///
/// The memory containing the output data is owned by EVM and has to be
/// freed with evm_result::release().
