you could for example create a skill to access your database for testing purposes and pass in your tables specifications so that the agent can easily retrieve data for you on the fly.
It is still worse as it consumes more context giving instructions for custom tooling whereas the LLM already understands how to connect to and query a read-only SQL service with standard tools
it’s also for (typically) longer context you don’t always want the agent to have in its context. if you always want it in context, use rules (memories)
but if it’s something more involved or less frequently used (perhaps some debugging methodology, or designing new data schemas) skills are probably a good fit