Bundesarchitektenkammer (BAK) - Practical guidelines for the implementation of the performance competition
Architectural services should always be awarded in a competition on the merits since they cannot be clearly described in advance. This is the only way to prevent a contracting body procuring bad planning by selecting the cheapest offer.
This guide from the Bundesarchitektenkammer (BAK) offers specific suggestions and templates which can be used as a basis for a services tender procedure beneath the VgV-treshold (Vergabeverordnung - public tendering regulation).
Source: https://bak.de/vergabe-von-planungsleistungen-unter-dem-vgv-schwellenwert/