CBOR is specified in a Standards-Track RFC. RFCs that serve as Internet Standards Documents are generated by the IETF based on an extensive technical review and quality control process. These are meant to last.
The stable reference.
Find the motivation for CBOR, the detailed specification (on 14 pages that include many examples), information on transcoding from and to JSON, and appendices with test vectors and readily usable code.
CBOR has been designed to be extensible by enabling third parties to define Tags. Immediately after CBOR was published, extensions started to be documented. Those that are completed are collected in an IANA registry to ensure specifications are available and that they don't stumble over each other.
Find pointers to what other people are also doing with CBOR, and extension specifications that might save you some work.