The gateway reads one validated AppConfig YAML file. How to scaffold it from a template, understand its top-level blocks, inject secrets safely, validate before boot, and reload without downtime.

How the gateway assembles its config from files, remote URLs, and inline base64 — the MCPG_CONFIG env var and the repeatable --config flag, how layers merge, how secrets resolve, and what hot-reloads.

MCPG negotiates two MCP revisions on one listener — the stateful 2025-11-25 release and the stateless 2026-07-28 revision. How version selection works, what changed between them, and why a single deployment serves both.

Make MCPG act as an MCP client to other MCP servers and re-serve their tools, resources, templates, and prompts under your own names, governance, and auth — one MCP endpoint that aggregates many upstreams.

Expose a gateway that binds no public port — it dials out to an MCPG relay and is answered through its own full request path. Get a public MCP URL for dev preview, reach a gateway behind NAT, or federate a customer's gateway so their secrets never leave their infrastructure.

Turn any tool into an interactive UI from config alone. The gateway ships one reviewed HTML bundle per kind and mints ui://mcpg/<id> resources from a declarative binding — no HTML, no plugin, no build step.

Worked, copy-pasteable recipes for the SQL backend (backend.kind sql) — reads, writes, upserts, streaming, fire-and-wait jobs, watch feeds, transactions, multi-tenancy, reporting, and ops probes across Postgres, MySQL, and SQLite.

Collapse a Flask/Express/FastAPI service that's a thin REST wrapper around a database into a direct MCPG SQL backend (backend.kind sql) — a before/after example, a step-by-step conversion, and what you gain and lose.