fix: count tokens from tool definitions when adjusting for context window

Signed-off-by: Grant Linville <grant@acorn.io>

Author: g-linville

pkg/openai/client.go

@@ -331,7 +331,12 @@ func (c *Client) Call(ctx context.Context, messageRequest types.CompletionReques
 			messageRequest.Messages[len(messageRequest.Messages)-1].Content = types.Text(TooLongMessage)
 		}
 
-		msgs = dropMessagesOverCount(messageRequest.MaxTokens, msgs)
+		toolsCount, err := countChatCompletionTools(messageRequest.Tools)
+		if err != nil {
+			return nil, err
+		}
+
+		msgs = dropMessagesOverCount(messageRequest.MaxTokens-toolsCount, msgs)
 	}
 
 	if len(msgs) == 0 {
@@ -447,14 +452,15 @@ func (c *Client) Call(ctx context.Context, messageRequest types.CompletionReques
 }
 
 func (c *Client) contextLimitRetryLoop(ctx context.Context, request openai.ChatCompletionRequest, id string, env []string, maxTokens int, status chan<- types.CompletionStatus) (types.CompletionMessage, error) {
-	var (
-		response types.CompletionMessage
-		err      error
-	)
+	toolsCount, err := countOpenAITools(request.Tools)
+	if err != nil {
+		return types.CompletionMessage{}, err
+	}
 
+	var response types.CompletionMessage
 	for range 10 { // maximum 10 tries
 		// Try to drop older messages again, with a decreased max tokens.
-		request.Messages = dropMessagesOverCount(maxTokens, request.Messages)
+		request.Messages = dropMessagesOverCount(maxTokens-toolsCount, request.Messages)
 		response, err = c.call(ctx, request, id, env, status)
 		if err == nil {
 			return response, nil

pkg/openai/count.go

@@ -1,7 +1,10 @@
 package openai
 
 import (
+	"encoding/json"
+
 	openai "github.com/gptscript-ai/chat-completion-client"
+	"github.com/gptscript-ai/gptscript/pkg/types"
 )
 
 const DefaultMaxTokens = 128_000
@@ -73,3 +76,29 @@ func countMessage(msg openai.ChatCompletionMessage) (count int) {
 	count += len(msg.ToolCallID)
 	return count / 3
 }
+
+func countChatCompletionTools(tools []types.ChatCompletionTool) (count int, err error) {
+	for _, t := range tools {
+		count += len(t.Function.Name)
+		count += len(t.Function.Description)
+		paramsJSON, err := json.Marshal(t.Function.Parameters)
+		if err != nil {
+			return 0, err
+		}
+		count += len(paramsJSON)
+	}
+	return count / 3, nil
+}
+
+func countOpenAITools(tools []openai.Tool) (count int, err error) {
+	for _, t := range tools {
+		count += len(t.Function.Name)
+		count += len(t.Function.Description)
+		paramsJSON, err := json.Marshal(t.Function.Parameters)
+		if err != nil {
+			return 0, err
+		}
+		count += len(paramsJSON)
+	}
+	return count / 3, nil
+}