AgentCrystal 

Core provider-neutral contracts for text and multimodal model access, embeddings, media values, generation, and live media sessions.

Text and multimodal tool registration, policy, and execution. Crystal supplies no concrete tools.

Text and multimodal model and tool loops with caller-configured limits.

Generic caller-owned middleware for typed asynchronous operations and event streams.

Middleware wrappers that preserve current Crystal client contracts and capability profiles.

Composition of named Agents with shared caller-configured limits.

Caller-defined typed workflow graphs with conditional edges and bounded concurrent steps.