The article is an attempt of a theoretical reflection on the agreements signed by two parties, with different relevance in political systems, in order to create a base of support for a minority government. The author try to answer the question whether such an agreement – in terms of transparency of a political system – is functional or dysfunctional for the stability of the Westminster democracy. He analyses the case of the 2017 agreement between the Conservative Party and Democratic Unionist Party using some system analysis and content analysis techniques. He concludes that in the case of the United Kingdom the process of forming an informal coalition in order to support the Theresa May’s minority government was typical for the democratic system, but the transactional nature of the agreement brought the British political system closer to patron-client patterns.