Compilers for reconfigurable computers aim to generate problem-specific optimized datapaths for kernels extracted from an input language. In many cases, however, judicious use of preexisting manually optimized IP blocks within these datapaths could improve the compute performance even further. The integration of IP blocks into the compiled datapaths poses a different set of problems than stitching together IPs to form a system-on-chip; though, instead of the loose coupling using standard busses employed by SoCs, the one between datapath and IP block must be much tighter. To this end, we propose a concise language that can be efficiently synthesized using a template-based approach for automatically generating lightweight data and control interfaces at the datapath level.