TSD is a part of the Shodor metadata system and it is responsible for keeping track of Interactivate textbooks, standards and dictionary words, as well as alignments between those items and
CSERD resources. Although the source of the data and the original purpose was for Interactive, the API can be used by any project that needs to keep track of alignments and relationships between
CSERD resources.
There is an admin tool available. It can be tested at https://newdev.shodor.org/tsd/.
This site provides API documentation and guides to using the API, as well as a conceptual overview for how TSD works. If you are looking at the internal version of this documentation, you will also see information on the internal TSD API and some other otherwise undocumented features.