Note: This is an English digest of the original Zenn post (Japanese). Read there for the full timeline and commit-level trace.
TL;DR
We ship tasteck, a B2B SaaS for the Japanese night-leisure industry (dispatch + cast shift management). 8 years of operational data, ~100 venues live.
Two days after the MCP design post, ChatGPT Plus can call our tools live: "Who's available tonight?" → MCP list_available_drivers → JSON → natural-language reply.
Estimated B2 OAuth sprint = 2 weeks (6/16–7/1). Actual = 1 day, by reading the spec carefully before touching code.
