Who pays
Whoever runs it. The API key on the call resolves a workspace and that workspace’s credits are spent. This is what makes publishing safe: a published API is executable by anyone, and every stranger’s run is billed to the stranger. The same rule applies to secrets, which always resolve from the caller.API keys
Create keys at console.notte.cc. One key identifies one workspace, which is why the credential also decides where an MCPbuild or run acts. Keep keys server-side.