outputschema-with-tool.go

outputschema-with-tool.go

package main

import (
	"context"
	"encoding/json"
	"log"
	"os"

	"google.golang.org/adk/agent"
	"google.golang.org/adk/agent/llmagent"
	"google.golang.org/adk/cmd/launcher"
	"google.golang.org/adk/cmd/launcher/full"
	"google.golang.org/adk/model"
	"google.golang.org/adk/model/gemini"
	"google.golang.org/adk/session"
	"google.golang.org/adk/tool"
	"google.golang.org/adk/tool/functiontool"
	"google.golang.org/genai"
)

func onBeforeModel(ctx agent.CallbackContext, req *model.LLMRequest) (*model.LLMResponse, error) {
	for _, tools := range req.Config.Tools {
		for _, decl := range tools.FunctionDeclarations {
			b, _ := json.MarshalIndent(decl, "", "  ")
			log.Printf("decl: %s", string(b))
		}
	}
	return nil, nil
}

func main() {
	ctx := context.Background()

	model, err := gemini.NewModel(ctx, "gemini-2.5-flash-lite", &genai.ClientConfig{
		APIKey: os.Getenv("GOOGLE_API_KEY"),
	})
	if err != nil {
		log.Fatalf("Failed to create model: %v", err)
	}

	type SumArgs struct {
		A int `json:"a"`
		B int `json:"b"`
	}
	type SumResult struct {
		Sum int `json:"sum"`
	}

	handler := func(ctx tool.Context, input SumArgs) (SumResult, error) {
		return SumResult{Sum: input.A + input.B}, nil
	}
	sumTool, err := functiontool.New(functiontool.Config{
		Name:        "sum",
		Description: "sums two integers",
	}, handler)
	if err != nil {
		log.Fatalf("Failed to create tool: %v", err)
	}

	a, err := llmagent.New(llmagent.Config{
		Name:        "root_agent",
		Model:       model,
		Description: "You can sum and multiply numbers.",
		Instruction: "Get the numbers and operations from the user and perform the calculations.",
		Tools: []tool.Tool{
			sumTool,
		},
		OutputKey: "result",
		OutputSchema: &genai.Schema{
			Type:        genai.TypeObject,
			Description: "Schema sum agent",
			Properties: map[string]*genai.Schema{
				"result": {
					Type:        genai.TypeNumber,
					Description: "The result of the sum.",
				},
			},
			Required: []string{"result"},
		},
		BeforeModelCallbacks: []llmagent.BeforeModelCallback{onBeforeModel},
	})

	config := &launcher.Config{
		AgentLoader:    agent.NewSingleLoader(a),
		SessionService: session.InMemoryService(),
	}

	l := full.NewLauncher()
	if err = l.Execute(ctx, config, os.Args[1:]); err != nil {
		log.Fatalf("Run failed: %v\n\n%s", err, l.CommandLineSyntax())
	}
}

# go build && ./outputschema-with-tool

User -> 41+1

Agent -> 
2025/12/27 13:05:02 decl: {
  "description": "Set your final response using the required output schema. Use this tool to provide your final structured answer instead of outputting text directly.",
  "name": "set_model_response",
  "parametersJsonSchema": {
    "description": "Schema sum agent",
    "properties": {
      "result": {
        "description": "The result of the sum.",
        "type": "NUMBER"
      }
    },
    "required": [
      "result"
    ],
    "type": "OBJECT"
  }
}
2025/12/27 13:05:02 decl: {
  "description": "sums two integers",
  "name": "sum",
  "parametersJsonSchema": {
    "type": "object",
    "required": [
      "a",
      "b"
    ],
    "properties": {
      "a": {
        "type": "integer"
      },
      "b": {
        "type": "integer"
      }
    },
    "additionalProperties": false
  },
  "responseJsonSchema": {
    "type": "object",
    "required": [
      "sum"
    ],
    "properties": {
      "sum": {
        "type": "integer"
      }
    },
    "additionalProperties": false
  }
}
{"result":42}