The substrates.io project is the reference implementation for the Humainary Substrates service provider interface (SPI). We have identified several concepts common to many library interfaces in designing open interfaces related to observability, diagnostics, and profiling over the last 20 years. To increase reusability and reliability while reducing cognitive load on adoptors and implementors, we have extracted and bundled the concepts into a packaging used across other Humainary projects, such as opensignals.io.