feat: support count tokens

config.go

@@ -18,11 +18,11 @@ const (
 type BetaVersion string
 
 const (
-	BetaTools20240404          BetaVersion = "tools-2024-04-04"
-	BetaTools20240516          BetaVersion = "tools-2024-05-16"
-	BetaPromptCaching20240731  BetaVersion = "prompt-caching-2024-07-31"
-	BetaMessageBatches20240924 BetaVersion = "message-batches-2024-09-24"
-
+	BetaTools20240404             BetaVersion = "tools-2024-04-04"
+	BetaTools20240516             BetaVersion = "tools-2024-05-16"
+	BetaPromptCaching20240731     BetaVersion = "prompt-caching-2024-07-31"
+	BetaMessageBatches20240924    BetaVersion = "message-batches-2024-09-24"
+	BetaTokenCounting20241101     BetaVersion = "token-counting-2024-11-01"
 	BetaMaxTokens35Sonnet20240715 BetaVersion = "max-tokens-3-5-sonnet-2024-07-15"
 )
 

count_tokens.go

@@ -0,0 +1,31 @@
+package anthropic
+
+import (
+	"context"
+	"net/http"
+)
+
+type CountTokensResponse struct {
+	httpHeader
+
+	InputTokens int `json:"input_tokens"`
+}
+
+func (c *Client) CountTokens(
+	ctx context.Context,
+	request MessagesRequest,
+) (response CountTokensResponse, err error) {
+	var setters []requestSetter
+	if len(c.config.BetaVersion) > 0 {
+		setters = append(setters, withBetaVersion(c.config.BetaVersion...))
+	}
+
+	urlSuffix := "/messages/count_tokens"
+	req, err := c.newRequest(ctx, http.MethodPost, urlSuffix, request, setters...)
+	if err != nil {
+		return
+	}
+
+	err = c.sendRequest(req, &response)
+	return
+}

integrationtest/count_tokens_test.go

@@ -0,0 +1,32 @@
+package integrationtest
+
+import (
+	"context"
+	"testing"
+
+	"github.com/liushuangls/go-anthropic/v2"
+)
+
+func TestCountTokens(t *testing.T) {
+	testAPIKey(t)
+	client := anthropic.NewClient(APIKey, anthropic.WithBetaVersion(anthropic.BetaTokenCounting20241101))
+	ctx := context.Background()
+
+	request := anthropic.MessagesRequest{
+		Model:       anthropic.ModelClaude3Dot5HaikuLatest,
+		MultiSystem: anthropic.NewMultiSystemMessages("you are an assistant", "you are snarky"),
+		Messages: []anthropic.Message{
+			anthropic.NewUserTextMessage("What is your name?"),
+			anthropic.NewAssistantTextMessage("My name is Claude."),
+			anthropic.NewUserTextMessage("What is your favorite color?"),
+		},
+	}
+
+	t.Run("CountTokens on real API", func(t *testing.T) {
+		resp, err := client.CountTokens(ctx, request)
+		if err != nil {
+			t.Fatalf("CountTokens error: %s", err)
+		}
+		t.Logf("CountTokens resp: %+v", resp)
+	})
+}

message.go

@@ -36,7 +36,7 @@ const (
 type MessagesRequest struct {
 	Model     Model     `json:"model"`
 	Messages  []Message `json:"messages"`
-	MaxTokens int       `json:"max_tokens"`
+	MaxTokens int       `json:"max_tokens,omitempty"`
 
 	System        string              `json:"-"`
 	MultiSystem   []MessageSystemPart `json:"-"`