The AMQP specification states in section 2.7.5 [1] about the message-format field of the Transfer performative:

This field MUST be specified for the first transfer of a multi-transfer message and can only be omitted for continuation transfers. It is an error if the message-format on a continuation transfer differs from the message-format on the first transfer of a delivery.

There are two things I would like the specification to be more explicit about:

• Whether the field is required on single transfer deliveries (see also AMQP-128).
• How to handle the error condition. Do we reject the message? Detach the Link? End the Session? Close the Connection? What ErrorCondition should be used?

[1] http://docs.oasis-open.org/amqp/core/v1.0/os/amqp-core-transport-v1.0-os.html#type-transfer