1package main
 2
 3// This example shows how to use provider-defined tools like Anthropic's
 4// built-in web search. Provider tools are executed server-side by the model
 5// provider, so there's no local tool implementation needed.
 6
 7import (
 8	"context"
 9	"fmt"
10	"os"
11	"strings"
12
13	"charm.land/fantasy"
14	"charm.land/fantasy/providers/anthropic"
15)
16
17func main() {
18	opts := []anthropic.Option{
19		anthropic.WithAPIKey(os.Getenv("ANTHROPIC_API_KEY")),
20	}
21	if baseURL := os.Getenv("ANTHROPIC_BASE_URL"); baseURL != "" {
22		opts = append(opts, anthropic.WithBaseURL(baseURL))
23	}
24
25	provider, err := anthropic.New(opts...)
26	if err != nil {
27		fmt.Fprintln(os.Stderr, "Error creating provider:", err)
28		os.Exit(1)
29	}
30
31	ctx := context.Background()
32
33	model, err := provider.LanguageModel(ctx, "claude-sonnet-4-20250514")
34	if err != nil {
35		fmt.Fprintln(os.Stderr, "Error creating model:", err)
36		os.Exit(1)
37	}
38
39	// Use the web search tool helper. Pass nil for defaults, or configure
40	// with options like MaxUses, AllowedDomains, and UserLocation.
41	webSearch := anthropic.WebSearchTool(nil)
42
43	agent := fantasy.NewAgent(model,
44		fantasy.WithProviderDefinedTools(webSearch),
45	)
46
47	result, err := agent.Generate(ctx, fantasy.AgentCall{
48		Prompt: "What is the current weather in San Francisco?",
49	})
50	if err != nil {
51		fmt.Fprintln(os.Stderr, "Error:", err)
52		os.Exit(1)
53	}
54
55	// Collect all text parts. With web search the model interleaves
56	// text around tool calls, producing multiple TextContent parts.
57	var text strings.Builder
58	for _, c := range result.Response.Content {
59		if tc, ok := c.(fantasy.TextContent); ok {
60			text.WriteString(tc.Text)
61		}
62	}
63	fmt.Println(text.String())
64
65	// Print any web sources the model cited.
66	for _, source := range result.Response.Content.Sources() {
67		fmt.Printf("Source: %s — %s\n", source.Title, source.URL)
68	}
69}