  In the setting of entanglement-assisted quantum error-correcting codes
(EAQECCs), the sender and the receiver have access to pre-shared entanglement.
Such codes promise better information rates or improved error handling
properties. Entanglement incurs costs and must be judiciously calibrated in
designing quantum codes with good performance, relative to their deployment
parameters.
  Revisiting known constructions, we devise tools from classical coding theory
to better understand how the amount of entanglement can be varied. We present
three new propagation rules and discuss how each of them affects the error
handling. Tables listing the parameters of the best performing qubit and qutrit
EAQECCs that we can explicitly construct are supplied for reference and
comparison.
