The general concept of good faith – a core concept of EU Member State laws (but not under common law jurisdictions – makes it largely superfluous to include a miscellaneous clause on ‘Further assurances’. Nevertheless, sometimes it may be helpful to provide for such ‘duty to cooperate’. For instance, the clause may support a party’s request when it must prove its rights under an agreement versus a third party, or if the enforcement of a party’s rights requires the fulfilment of any legal or practical formality. As an example of such a clause:
Further assurance. Each Party shall cooperate with the other and execute such instruments or documents and take such other actions as may reasonably be requested from time to time in order to carry out, evidence or confirm their rights or obligations or as may be reasonably necessary or helpful to give effect to this Agreement.
Note: if you delete the clause in a mark-up on the other party’s first draft, or if the other party deletes yours, this may convey a sense of unwillingness to cooperate.