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Constraint the output format

Use these options if you want to constrain the model's output format. It can be useful, for example, if you want the model return a JSON with a specific structure.

  • WithResponseTextFormat

It is the default option (you unlikely need to specify it). Instruct the model that the expected response format is a text (without any specific structure, unless if it is specified in the prompt).

  • WithResponseJsonObjectFormat

This option instructs the model that the expected response format is a JSON object but without any specific structure. You can specify the expected structure in your prompt.

Then, use the method Output to parse the JSON object.

Example:

req := mistral.NewChatCompletionRequest("mistral-small-latest",
    mistral.BaseMessage{
        mistral.NewUserMessageFromString("Tell me a joke about cats. Return a JSON object with a 'joke field'."),
    },
    mistral.WithResponseJsonObjectFormat())
res, err := client.ChatCompletion(ctx, req)

msg := res.AssistantMessage()

var joke map[string]any // (1)
if err := msg.Output(&joke); err != nil {
    // handle error
}

  1. Here, you can use a plain struct type instead

  2. WithResponseJsonSchema

This option instructs the model that the expected response format is a JSON object with a specific structure. You can optionally specify a description for each field. That will help the model to figure out how to fill each field.

You can then use the method Output to parse the JSON object.

Example:

req := mistral.NewChatCompletionRequest("mistral-small-latest", 
    messages, 
    mistral.WithResponseJsonSchema(mistral.NewObjectPropertyDefinition(
        map[string]mistral.PropertyDefinition{
            "joke":        {Type: "string", Description: "A joke."}, 
            "laugh_level": {
                Type: "integer", 
                Description: "How funny is the joke? In percentage.",
                Default: 50},
        },
    )))

msg := res.AssistantMessage()

var joke map[string]any
if err := msg.Output(&joke); err != nil {
    // handle error
}

Check the following example