tool-scripting

Plug-n-play "code mode" tool call scripting for Vercel AI SDK

Inspired by Cloudflare's Code Mode - LLMs are better at writing JavaScript than using synthetic tool calling syntax.

Installation

npm install tool-scripting ai@5 zod@4

Note: Requires Zod v4

Usage

import{z}from'zod';import{generateText,tool,stepCountIs}from'ai';import{openai}=from'@ai-sdk/openai';import{toolScripting}from'tool-scripting';consttools={getUserLocation: tool({description: 'Get user current location',inputSchema: z.object({}),outputSchema: z.string(),// optional outputSchema to help the LLM compose tool callsexecute: async()=>'San Francisco, CA',}),getWeather: tool({description: 'Get weather for a location',inputSchema: z.object({location: z.string(),}),outputSchema: z.object({// optional outputSchema to help the LLM compose tool callstemperature: z.number(),condition: z.string(),}),execute: async({ location })=>{return{ location,temperature: 65,condition: 'foggy'};},}),};// Just wrap your existing streamText (or generateText)constbetterGenerateText=toolScripting(streamText)// Same familiar AI SDK usageconstresult=awaitbetterStreamText({model: openai('gpt-5'),
tools,messages: [{role: 'assistant',content: 'How can I help?'},{role: 'user',content: 'Check the weather near me'},],stopWhen: stepCountIs(5),});

How it works

1. Converts your tool definitions to a tool call SDK
2. LLM Generates JavaScript code instead of tool calls
3. Executes code in secure sandbox (v8 isolate) with tool bindings
4. Returns whatever the generated code returns

Why Code Mode?

Tool Scripting > Tool Calls

• 🧠 Better - LLMs excel at JavaScript vs synthetic tool syntax
• 🔧 Composable - Logic and conditionals between tool calls
• 🔒 Secure - Sandboxed execution with controlled bindings
• 🎯 Simple - Just wrap your existing Vercel AI SDK calls

Example

Here's what a traditional series of tool calls looks like (without Tool Scripting):

role: user
text: Check the weather near me
--
role: assistant
type: tool-call
toolName: getUserLocation
--
role: tool
type: tool-result
output: San Francisco, CA
--
role: assistant
type: tool-call
toolName: getWeather
input:
location: San Francisco, CA
--
role: tool
type: tool-result
output:
temperature: 65
condition: foggy
--
role: assistant
text: The weather in San Francisco, CA today is foggy with a temperature of 65°F.

Now, here's the same process with Tool Scripting:

role: user
text: Check the weather near me
--
role: assistant
type: tool-call
toolName: runToolScript
input:
script: const location = await getUserLocation();\nconst weather = await getWeather({ location });\nreturn { location, weather };
--
role: tool
type: tool-result
output:
location: San Francisco, CA
weather:
temperature: 65
condition: foggy
--
role: assistant
text: The weather in San Francisco, CA today is foggy with a temperature of 65°F.

💥 In a single LLM step, we composed two tools to get the user's location and then the weather for that location.

Requirements

• Node.js 18+
• Vercel AI SDK (ai package) v5+
• Zod v4+ (for built-in JSON Schema conversion)
• Tools using tool() helper with execute functions

Works with both TypeScript and JavaScript.

License

MIT