I built a small MCP server for the ChatGPT Ads advertiser API, which OpenAI opened to the public a couple of weeks ago.It s read-only for now: accounts, campaigns, ad groups, ads and insights (11 tools in total). You can query campaigns from Claude, Codex, Cursor and so on in plain language. Writes ( actions ) are next; I have two ideas here: - wrap them in a deterministic tool (json in/out) - add a human in the loop (maybe even a verification/consistency check step between query and tool/json output)Claude Code did most of the work but it wasn t a one-shot. The OpenAI API spec is very clean though and easy to understand; for some reason Claude couldn t read OpenAI s own docs, so I ended up with some manual copy paste .Also I iterated a bit and went from a local stdio install to npm and then made it available in the MCP registry.Feedback welcome, especially on the write/elicitation side and on hosting a remote version.PS: It s (obviously) unofficial and not affiliated with OpenAI.