There were 2 reasons I had for building this:

1. I wanted to genuinely evaluate MCP as a protocol. Verdict: I think it's unnecessary complexity. Could have used OpenAPI or GraphQL, but here we are...

2. Lots of people probably want to run queries on data. Apache Calcite is an under-utilized tool for this, because of how much leverage you get for relatively little implementation code.

Also, my dayjob work is on a product that does a similar sort of thing, and I wanted to get a feel for how the quality of a naive implementation would be in comparison.