prap

A lightweight agent harness.

pip install prap

import asyncio
from prap import run


def model(messages):
    if messages[-1]["role"] == "tool":
        return {"content": "The answer is " + messages[-1]["content"]}
    return {
        "tool_calls": [
            {"id": "sum-1", "name": "add", "arguments": {"a": 2, "b": 3}}
        ]
    }


transcript = asyncio.run(run(
    model,
    [{"role": "user", "content": "What is 2 + 3?"}],
    {"add": lambda args: args["a"] + args["b"]},
))
print(transcript[-1]["content"])

Supply your own model callback or API adapter. Callbacks may be synchronous or asynchronous. The model receives a copy of the transcript and returns an object with a string content (default "") and an optional tool_calls list. Each call has a nonempty string id, a registered name, and an arguments object. Each tool receives that object as one positional argument and returns a JSON value.

Calls in a batch run sequentially after the entire batch is validated. A response without tool calls ends the run. max_turns defaults to 8 and limits model calls; tools requested on the last turn still run. An unfinished run raises TurnLimitError. Callback exceptions propagate without retries. Messages and results must be JSON serializable; non-finite numbers are rejected.

Requires Python 3.10 or newer. No runtime dependencies.

Licensed under Apache-2.0.