In this first document, after a brief Introduction (Section 1), we are describing the rationale for QMCkl design guidelines (Section 2). In particular, objectives and general methodology will be highlighted. Then, more precise details on the methodology will be given by walking through a detailed DGEMM example (Section 3). Finally, some preliminary performance results on a key QMCkl routine (JASTROW computation will be given). This first document essentially covers work in progress. As such, first, many implementation choices presented in this first document are still preliminary and might evolve. Second, we first focused on multicore CPU: although we kept in mind GPU constraints and issues, most of the implementation efforts targeted multicore CPU (X86 and ARM) and the first performance results have been obtained on X86. More performance tests on X86 are underway, and tests on ARM will be carried out in the coming months as well as the first QMCkl extensions to cover GPU. All of these topics will be covered in detail in the second deliverable.