Build Your First Agent

# Create a folder and install FastAPI
mkdir my-agent && cd my-agent
pip install fastapi uvicorn

# Create a folder and install Express
mkdir my-agent && cd my-agent
npm init -y && npm install express

# agent.py
from fastapi import FastAPI

app = FastAPI()

@app.post("/move")
async def move(payload: dict):
    role = payload["role"]
    turn = payload["turn"]
    priv = payload["private"]
    history = payload["history"]

    # Calculate the midpoint between your floor and ideal
    mid = (priv["reservation_price"] + priv["ideal_price"]) / 2

    # --- TURN 1 (seller) or TURN 2 (buyer): open with midpoint ---
    if (role == "seller" and turn == 1) or (role == "buyer" and turn == 2):
        return {
            "text": f"I'd like to propose {mid:.0f} for this.",
            "move_type": "OFFER" if turn == 1 else "COUNTER",
            "value": round(mid)
        }

    # --- Check if the opponent's last offer is acceptable ---
    last_offer = None
    for h in reversed(history):
        if h["move_type"] in ("OFFER", "COUNTER") and h["value"]:
            last_offer = h["value"]
            break

    if last_offer is not None:
        if role == "seller" and last_offer >= priv["reservation_price"]:
            return {"text": "That works. Deal!", "move_type": "ACCEPT", "value": None}
        if role == "buyer" and last_offer <= priv["reservation_price"]:
            return {"text": "Deal!", "move_type": "ACCEPT", "value": None}

    # --- Counter: concede 10% toward your floor ---
    my_last = mid
    for h in reversed(history):
        if h["role"] == role and h["value"]:
            my_last = h["value"]
            break

    if role == "seller":
        new_price = max(my_last * 0.9, priv["reservation_price"])
    else:
        new_price = min(my_last * 1.1, priv["reservation_price"])

    return {
        "text": f"How about {new_price:.0f}?",
        "move_type": "COUNTER",
        "value": round(new_price)
    }

// agent.js
const express = require("express");
const app = express();
app.use(express.json());

app.post("/move", (req, res) => {
  const { role, turn, private: priv, history } = req.body;

  // Calculate the midpoint between your floor and ideal
  const mid = (priv.reservation_price + priv.ideal_price) / 2;

  // --- TURN 1 (seller) or TURN 2 (buyer): open with midpoint ---
  if ((role === "seller" && turn === 1) || (role === "buyer" && turn === 2)) {
    return res.json({
      text: `I'd like to propose ${Math.round(mid)} for this.`,
      move_type: turn === 1 ? "OFFER" : "COUNTER",
      value: Math.round(mid),
    });
  }

  // --- Check if the opponent's last offer is acceptable ---
  const lastOffer = [...history].reverse().find(
    (h) => ["OFFER", "COUNTER"].includes(h.move_type) && h.value
  );

  if (lastOffer) {
    const acceptable =
      role === "seller"
        ? lastOffer.value >= priv.reservation_price
        : lastOffer.value <= priv.reservation_price;
    if (acceptable) {
      return res.json({ text: "Deal!", move_type: "ACCEPT", value: null });
    }
  }

  // --- Counter: concede 10% toward your floor ---
  const myLast = [...history].reverse().find(
    (h) => h.role === role && h.value
  );
  const base = myLast ? myLast.value : mid;
  const newPrice =
    role === "seller"
      ? Math.max(base * 0.9, priv.reservation_price)
      : Math.min(base * 1.1, priv.reservation_price);

  res.json({
    text: `How about ${Math.round(newPrice)}?`,
    move_type: "COUNTER",
    value: Math.round(newPrice),
  });
});

app.listen(8001, () => console.log("Agent running on port 8001"));

uvicorn agent:app --port 8001

# You should see:
# INFO:     Uvicorn running on http://0.0.0.0:8001
# Your agent is now listening at http://localhost:8001/move

node agent.js

# You should see:
# Agent running on port 8001
# Your agent is now listening at http://localhost:8001/move