analyse_chess_position_tool.py

from langchain_core.tools import tool
import requests

@tool
def get_best_move(fen: str) -> str:
    """
    Given the description of a chess board using FEN notation, returns the next best move. 
    
    Args:
        fen (str): The description of the chessboard position in FEN notation.
        
    Returns:
        str: The description of the next best move.
    """
    url = "https://lichess.org/api/cloud-eval"
    params = {
        "fen": fen,
        "multiPv": 1,  # only top move
        "syzygy": 5    # enable tablebase for 5-piece positions
    }

    response = requests.get(url, params=params)

    if response.status_code != 200:
        return f"API error: {response.status_code} - {response.text}"

    data = response.json()
    if not data.get("pvs"):
        return "No best move found."

    best_line = data["pvs"][0]
    score = best_line["cp"] if "cp" in best_line else f"Mate in {best_line.get('mate')}"
    move = best_line["moves"].split()[0]

    # Optional: threshold to define a "guaranteed win"
    if "mate" in best_line or best_line.get("cp", 0) > 500:
        return move

    return f"No clearly winning move. Best suggestion: {move} (score: {score})"