The Consensus CDS (CCDS) project is a collaborative effort to identify a core set of human and mouse protein coding regions that are consistently annotated and of high quality. The long term goal is to support convergence towards a standard set of gene annotations.
https://www.ncbi.nlm.nih.gov/projects/CCDS/CcdsBrowse.cgi
The mapping from CCDS ids to gene ids can be found from:
https://ftp.ncbi.nlm.nih.gov/pub/CCDS (human and mouse)
e.g. in CCDS_current.txt file
or from
RefSeq records in GenePept format
e.g. NP_689699.3
Since we might have already parsed RefSeq files, the RefSeq option might be a bit more efficient to get the data into MyGene.info