toolloop

Agent loops for LLM providers without native tool use.

toolloop is a Python framework for building autonomous agents — tool use, exploration, coding — on top of any LLM endpoint, even (especially) the ones whose SDK never exposed a tools parameter. If you can send messages and get text back, you can run an agent on it.

Why it exists

Plenty of real-world LLM access goes through proprietary corporate SDKs that proxy the big providers (Anthropic, OpenAI, Kimi, DeepSeek, ...) but strip or never implemented the tool-use layer. The models behind them are perfectly capable of agentic work — the SDK just won't carry function calls.

toolloop solves this at the application layer:

• Bring your own provider. The framework never manages providers. The whole contract is one async method: complete(messages) -> str.
• Tools over plain text. Tool schemas are rendered into the system prompt; tool calls are parsed out of the model's text responses. Parse errors are fed back to the model (auto-repair) until the envelope is right.
• Loop until satisfied. Given an input, the agent calls tools, receives observations, and iterates until it emits a final_answer.

A taste

import asyncio

from toolloop import Agent, tool


@tool
async def add(a: int, b: int) -> int:
    """Add two numbers."""
    return a + b


class DemoProvider:  # scripted: stands in for your real provider
    def __init__(self):
        self.turns = [
            '{"type": "tool_call", "calls": [{"id": "c1", "name": "add", "args": {"a": 2, "b": 3}}]}',
            '{"type": "final_answer", "output": "2 + 3 = 5"}',
        ]

    async def complete(self, messages):
        return self.turns.pop(0)


agent = Agent(DemoProvider(), tools=[add])
result = asyncio.run(agent.run("how much is 2 + 3?"))
print(result.output)  # 2 + 3 = 5

Runs offline, with zero API keys — start in Getting started.

Where to go next

• Getting started — install, first agent, first provider
• The agent loop — envelopes, auto-repair, stop conditions
• Production — retries, rate limiting, checkpoints, observability
• Examples — nine runnable, offline examples and two full apps