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Jun 2025 (v0.3.4)

Mochi v0.3.4 introduces tool calling, union types, and inline methods, enabling richer integrations and more expressive type definitions.

Tool Calling​

generate blocks can now invoke registered tools. Each tool may include a description used by the LLM when deciding to call it.

fun getWeather(city: string): string {
  return "Clear"
}

let reply = generate text {
  prompt: "Weather in Paris?"
  tools: [
    getWeather { description: "Lookup current weather" }
  ]
}

Union Types​

Programs may declare algebraic data types using the type A = ... | ... syntax. Pattern matching integrates seamlessly with these unions.

type Tree =
  Leaf
  | Node(left: Tree, value: int, right: Tree)

let total = match someTree {
  Leaf => 0
  Node(l, v, r) => v + total(l) + total(r)
}

Inline Methods​

Struct types can embed function members that act as methods:

type Circle {
  radius: float

  fun area(): float {
    return 3.14 * radius * radius
  }
}

Other Changes​

  • Tool descriptions exported in JSON schemas
  • Examples extended with method and binary tree demos
  • Fixed several issues around tool call handling