In French urban planning, private engineering actors play an increasing role in the implementation of public policies, especially in urban projects. At times considered as “experts”, these invisible elements of projects are known for assisting local authorities on technical aspects. Based on an ethnographic investigation in a middle-sized company (500 employees), this paper describes the work and market position of engineering firms and the mutations they meet. These actors argue that the world encounters a complexification that requires new methods instead of the neutral and rigid manners of an expert. As such, they promote adaptation, challenging the demand and long-term support of client instead of a punctual and bordered missions. Thus, they develop a new position of consultant to transform the executive relationship into a partnership. They promise to “complete the project” of their client, allowing them to get new missions, particularly on the urban consulting market. Consequently, consultants rather than scientific experts, they access information and give advice differently. Gathering information does not necessarily imply a rational method with measures or analysis. To be faster, they prefer finding a good representative, source of synthetic and relevant information. The final report is not the only result of the service offered. They perform an important organizational work of the project process, consisting in preparing discussion and consultation instances and finally choosing who can have a voice in the projects. Ultimately, by promoting dialogue and exchange instead of expertise, they increase their power in urban policies.