feat: Add tool calling support in ChatOllama

[davidmigloz]

Tool calling allows a model to respond to a given prompt by generating output that matches a user-defined schema, that you can then use to call the tools in your code and return the result back to the model to complete the conversation.

Notes:

• Tool calling requires Ollama 0.2.8 or newer.
• Streaming tool calls is not supported at the moment.
• Not all models support tool calls. Check the Ollama catalogue for models that have the Tools tag (e.g. llama3.1).

Check the docs for more information on how to use tools.

const tool = ToolSpec(
  name: 'get_current_weather',
  description: 'Get the current weather in a given location',
  inputJsonSchema: {
    'type': 'object',
    'properties': {
      'location': {
        'type': 'string',
        'description': 'The city and country, e.g. San Francisco, US',
      },
    },
    'required': ['location'],
  },
);

final chatModel = ChatOllama(
  defaultOptions: ChatOllamaOptions(
    model: 'llama3.1',
    temperature: 0,
    tools: [tool],
  ),
);

final res = await chatModel.invoke(
  PromptValue.string('What’s the weather like in Boston and Madrid right now in celsius?'),
);
print(res.output.toolCalls);
// [AIChatMessageToolCall{
//   id: a621064b-03b3-4ca6-8278-f37504901034,
//   name: get_current_weather,
//   arguments: {location: Boston, US},
// }, 
// AIChatMessageToolCall{
//   id: f160d9ba-ae7d-4abc-a910-2b6cd503ec53,
//   name: get_current_weather,
//   arguments: {location: Madrid, ES},
// }]