Add support for Anthropic Claude models

.gitignore

@@ -20,3 +20,5 @@ profile.cov
 # Go workspace file
 go.work
 go.work.sum
+
+.env

examples/anthropic/main.go

@@ -0,0 +1,100 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package provides an example ADK agent using Anthropic Claude.
+//
+// Run with:
+//
+//	godotenv go run ./examples/anthropic
+//
+// Environment variables:
+//   - ANTHROPIC_API_KEY: API key for direct Anthropic API access
+//   - ANTHROPIC_USE_VERTEX: Set to "true" or "1" to use Vertex AI backend
+//   - GOOGLE_CLOUD_PROJECT: GCP project ID (required for Vertex AI)
+//   - GOOGLE_CLOUD_REGION: GCP region (required for Vertex AI)
+package main
+
+import (
+	"context"
+	"log"
+	"os"
+
+	anthropicsdk "github.com/anthropics/anthropic-sdk-go"
+
+	"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/anthropic"
+	"google.golang.org/adk/tool"
+	"google.golang.org/adk/tool/functiontool"
+)
+
+// WeatherInput is the input schema for the weather tool.
+type WeatherInput struct {
+	City string `json:"city" jsonschema:"the city name to get weather for"`
+}
+
+// WeatherOutput is the output schema for the weather tool.
+type WeatherOutput struct {
+	Weather string `json:"weather"`
+}
+
+// getWeather is a simple tool function for the agent to call.
+func getWeather(_ tool.Context, input WeatherInput) (WeatherOutput, error) {
+	// In a real application, this would call a weather API
+	weather := "The weather in " + input.City + " is sunny with a temperature of 22°C."
+	return WeatherOutput{Weather: weather}, nil
+}
+
+func main() {
+	ctx := context.Background()
+
+	// Create the Anthropic model.
+	// By default, uses the ANTHROPIC_API_KEY environment variable.
+	// Set ANTHROPIC_USE_VERTEX=true to use Vertex AI backend instead.
+	model, err := anthropic.NewModel(ctx, anthropicsdk.ModelClaudeHaiku4_5, nil)
+	if err != nil {
+		log.Fatalf("Failed to create model: %v", err)
+	}
+
+	// Create a function tool for the agent
+	weatherTool, err := functiontool.New(functiontool.Config{
+		Name:        "get_weather",
+		Description: "Get the current weather for a city",
+	}, getWeather)
+	if err != nil {
+		log.Fatalf("Failed to create tool: %v", err)
+	}
+
+	a, err := llmagent.New(llmagent.Config{
+		Name:        "anthropic_weather_agent",
+		Model:       model,
+		Description: "Agent to answer questions about the weather in a city using Anthropic Claude.",
+		Instruction: "You are a helpful weather assistant. When asked about weather, use the get_weather tool to fetch current conditions. Be concise in your responses.",
+		Tools:       []tool.Tool{weatherTool},
+	})
+	if err != nil {
+		log.Fatalf("Failed to create agent: %v", err)
+	}
+
+	config := &launcher.Config{
+		AgentLoader: agent.NewSingleLoader(a),
+	}
+
+	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())
+	}
+}

examples/workflowagents/loop-anthropic/main.go

@@ -0,0 +1,113 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package demonstrates a workflow agent that runs an Anthropic-powered agent in a loop.
+//
+// Run with:
+//
+//	godotenv go run ./examples/workflowagents/loop-anthropic
+//
+// Environment variables:
+//   - ANTHROPIC_API_KEY: API key for direct Anthropic API access
+package main
+
+import (
+	"context"
+	"log"
+	"os"
+
+	"google.golang.org/adk/agent"
+	"google.golang.org/adk/agent/llmagent"
+	"google.golang.org/adk/agent/workflowagents/loopagent"
+	"google.golang.org/adk/cmd/launcher"
+	"google.golang.org/adk/cmd/launcher/full"
+	"google.golang.org/adk/model/anthropic"
+	"google.golang.org/adk/tool"
+	"google.golang.org/adk/tool/functiontool"
+
+	anthropicsdk "github.com/anthropics/anthropic-sdk-go"
+)
+
+// StoryInput is the input for the continue_story tool.
+type StoryInput struct {
+	Direction string `json:"direction" jsonschema:"the direction to take the story (e.g., 'add conflict', 'introduce character', 'resolve plot')"`
+}
+
+// StoryOutput is the output of the continue_story tool.
+type StoryOutput struct {
+	Instruction string `json:"instruction"`
+}
+
+// continueStory provides story direction to the agent.
+func continueStory(_ tool.Context, input StoryInput) (StoryOutput, error) {
+	return StoryOutput{
+		Instruction: "Continue the story by: " + input.Direction,
+	}, nil
+}
+
+func main() {
+	ctx := context.Background()
+
+	// Create the Anthropic model
+	model, err := anthropic.NewModel(ctx, anthropicsdk.ModelClaudeOpus4_5, nil)
+	if err != nil {
+		log.Fatalf("Failed to create model: %v", err)
+	}
+
+	// Create a tool for story continuation
+	storyTool, err := functiontool.New(functiontool.Config{
+		Name:        "continue_story",
+		Description: "Get instructions for continuing the story in a specific direction",
+	}, continueStory)
+	if err != nil {
+		log.Fatalf("Failed to create tool: %v", err)
+	}
+
+	// Create an LLM agent that tells stories
+	storyteller, err := llmagent.New(llmagent.Config{
+		Name:        "storyteller",
+		Model:       model,
+		Description: "A creative storyteller that writes short story segments.",
+		Instruction: `You are a creative storyteller. Each time you are called, continue the ongoing story with 2-3 sentences.
+Build upon what came before, adding new elements while maintaining narrative coherence.
+Keep each segment brief but engaging. Do not repeat previous content.
+If this is the first segment, begin a new story about an unexpected adventure.`,
+		Tools: []tool.Tool{storyTool},
+	})
+	if err != nil {
+		log.Fatalf("Failed to create storyteller agent: %v", err)
+	}
+
+	// Create a loop agent that runs the storyteller multiple times
+	loopAgent, err := loopagent.New(loopagent.Config{
+		MaxIterations: 3,
+		AgentConfig: agent.Config{
+			Name:        "story_loop",
+			Description: "A loop agent that builds a story over multiple iterations using Anthropic Claude",
+			SubAgents:   []agent.Agent{storyteller},
+		},
+	})
+	if err != nil {
+		log.Fatalf("Failed to create loop agent: %v", err)
+	}
+
+	config := &launcher.Config{
+		AgentLoader: agent.NewSingleLoader(loopAgent),
+	}
+
+	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())
+	}
+}

examples/workflowagents/parallel-anthropic/main.go

@@ -0,0 +1,98 @@
+// Copyright 2025 Google LLC
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+// Package demonstrates a workflow agent that runs Anthropic-powered sub-agents in parallel.
+//
+// Run with:
+//
+//	godotenv go run ./examples/workflowagents/parallel-anthropic
+//
+// Environment variables:
+//   - ANTHROPIC_API_KEY: API key for direct Anthropic API access
+package main
+
+import (
+	"context"
+	"log"
+	"os"
+
+	anthropicsdk "github.com/anthropics/anthropic-sdk-go"
+
+	"google.golang.org/adk/agent"
+	"google.golang.org/adk/agent/llmagent"
+	"google.golang.org/adk/agent/workflowagents/parallelagent"
+	"google.golang.org/adk/cmd/launcher"
+	"google.golang.org/adk/cmd/launcher/full"
+	"google.golang.org/adk/model/anthropic"
+)
+
+func main() {
+	ctx := context.Background()
+
+	// Create the Anthropic model
+	model, err := anthropic.NewModel(ctx, anthropicsdk.ModelClaudeSonnet4_20250514, nil)
+	if err != nil {
+		log.Fatalf("Failed to create model: %v", err)
+	}
+
+	// Create two LLM agents that will run in parallel
+	// Each agent has a different perspective on the same topic
+
+	optimistAgent, err := llmagent.New(llmagent.Config{
+		Name:        "optimist_agent",
+		Model:       model,
+		Description: "An optimistic analyst that focuses on opportunities.",
+		Instruction: `You are an optimistic business analyst. When given a topic or question,
+provide a brief (2-3 sentences) analysis focusing on the positive aspects, opportunities,
+and potential benefits. Be concise but insightful.`,
+		OutputKey: "optimist_view",
+	})
+	if err != nil {
+		log.Fatalf("Failed to create optimist agent: %v", err)
+	}
+
+	pessimistAgent, err := llmagent.New(llmagent.Config{
+		Name:        "pessimist_agent",
+		Model:       model,
+		Description: "A cautious analyst that focuses on risks.",
+		Instruction: `You are a cautious risk analyst. When given a topic or question,
+provide a brief (2-3 sentences) analysis focusing on potential risks, challenges,
+and things to watch out for. Be concise but thorough.`,
+		OutputKey: "pessimist_view",
+	})
+	if err != nil {
+		log.Fatalf("Failed to create pessimist agent: %v", err)
+	}
+
+	// Create a parallel agent that runs both analysts simultaneously
+	parallelAgent, err := parallelagent.New(parallelagent.Config{
+		AgentConfig: agent.Config{
+			Name:        "dual_perspective_agent",
+			Description: "Analyses topics from both optimistic and pessimistic perspectives in parallel",
+			SubAgents:   []agent.Agent{optimistAgent, pessimistAgent},
+		},
+	})
+	if err != nil {
+		log.Fatalf("Failed to create parallel agent: %v", err)
+	}
+
+	config := &launcher.Config{
+		AgentLoader: agent.NewSingleLoader(parallelAgent),
+	}
+
+	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())
+	}
+}