In the co-op mode you can talk to the AI teammate in natural language (“focus the right cultist”), and it uses recent conversation in later decisions. Which tool-calling, vision and streaming features work depends on the model provider.
Projects / Bot / agent
STS2-Agent
Slay the Spire 2 mod with a local HTTP API, an MCP endpoint and an in-game overlay (F8) that drives any OpenAI-compatible model. It can launch a second game instance where the model plays as your co-op teammate.