vercel-ai-sdk 0.0.1.dev10

The AI Toolkit for Python

ai

[!WARNING] This framework is experimental. It is not stable and is not guaranteed to be maintained in the future. For evaluation purposes only.

Python toolkit for building model-powered apps and agent loops.

Install

uv add vercel-ai-sdk

import ai

Quick Start

import asyncio

import ai


@ai.tool
async def get_weather(city: str) -> str:
    """Get the current weather for a city."""
    return f"Sunny, 72F in {city}"


async def main() -> None:
    model = ai.ai_gateway("anthropic/claude-sonnet-4")
    agent = ai.agent(tools=[get_weather])

    messages = [
        ai.system_message("You are a helpful weather assistant."),
        ai.user_message("What's the weather in Tokyo?"),
    ]

    async for msg in agent.run(model, messages):
        if msg.text_delta:
            print(msg.text_delta, end="", flush=True)
    print()


if __name__ == "__main__":
    asyncio.run(main())

API Surface

Models

ai.openai(model_id)             provider — callable, returns Model
ai.anthropic(model_id)          provider — callable, returns Model
ai.ai_gateway(model_id)         provider — callable, returns Model
provider.list()                 list available model IDs from the provider API
ai.stream(model, messages, ...) streaming generation (supports tools=, output_type=)
ai.generate(model, messages, p) non-streaming generation (ImageParams, VideoParams)
ai.check_connection(model)      verify credentials and model availability
ai.Client(base_url=, api_key=)  explicit client — pass to provider call: ai.openai("gpt-5.4", client=c)

Agents

ai.agent(tools=[...])           agent with tool loop
ai.tool                         decorator: schema gen + validation + execution
ai.hook(name, payload=, ...)    suspension point; resolve with ai.resolve_hook(...)
ai.resolve_hook(name, value)    resolve a pending hook from outside the loop
ai.cancel_hook(name)            cancel a pending hook
ai.yield_from(...)              forward nested agent / streaming tool output

Messages

ai.system_message  ai.user_message  ai.assistant_message  ai.tool_message
ai.tool_result     ai.file_part     ai.thinking

Middleware

ai.Middleware                    base class — subclass and override wrap methods
agent.run(..., middleware=[m])   run-scoped, first = outermost

Five wrap surfaces: wrap_agent_run, wrap_model, wrap_generate, wrap_tool, wrap_hook. Each receives a context dataclass and a next callable. Default implementations pass through.

Integrations

ai.mcp.get_http_tools(url, ...) expose an MCP server as tools
ai.ai_sdk_ui                    AI SDK UI streaming adapter

Custom Agent Loops

Override the default loop when you need approval gates, routing, or custom orchestration:

@agent.loop
async def custom(context: ai.Context):
    while True:
        s = await ai.stream(
            context.model, context.messages, tools=context.tools
        )
        async for msg in s:
            yield msg

        tool_calls = context.resolve(s.tool_calls)
        if not tool_calls:
            return

        results = [await tc() for tc in tool_calls]
        yield ai.tool_message(*results)

Examples

Small focused samples live in examples/samples/. End-to-end demos:

• examples/fastapi-vite/ -- FastAPI backend + Vite frontend with hook-based tool approval
• examples/multiagent-textual/ -- Textual TUI with parallel agents and interactive hook resolution
• examples/temporal-direct/ -- durable agent with a custom loop (every I/O call is a Temporal activity)
• examples/temporal-middleware/ -- durable agent via middleware (default loop, I/O routed to Temporal activities)
• examples/samples/middleware_simple.py -- middleware that logs all five execution surfaces