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Generative AI > Google Gemini API > Carrier Selection Agent

Carrier Selection Agent

Author: Venkata Sudhakar

ShopMax India ships to every corner of India - metro cities, tier-2 towns, and remote pincodes. Different carriers have different strengths: BlueDart is fast but expensive, Delhivery has the broadest reach, DTDC is cost-effective for heavy items. Choosing the right carrier for each shipment manually is impossible at scale. An automated carrier selection agent that applies business rules to pick the best carrier for every order optimises cost and delivery speed simultaneously.

This tutorial builds a Carrier Selection Agent using ADK and Gemini. The agent takes shipment details - pincode, weight, declared value, and SLA - queries carrier capabilities, and recommends the optimal carrier with justification.

The below example shows carrier selection for ShopMax India outbound shipments.

from google.adk.agents import LlmAgent
from google.adk.tools import FunctionTool
from google.adk.runners import Runner
from google.adk.sessions import InMemorySessionService

# --- Carrier capabilities and rates ---
CARRIERS = {
    "BlueDart": {
        "max_weight_kg": 70,
        "rate_per_kg": 65,
        "min_charge": 120,
        "transit_days_metro": 1,
        "transit_days_tier2": 2,
        "transit_days_remote": 4,
        "cod_available": True,
        "max_declared_value": 500000,
        "pincodes_served": "metro+tier2+select_remote",
    },
    "Delhivery": {
        "max_weight_kg": 50,
        "rate_per_kg": 45,
        "min_charge": 80,
        "transit_days_metro": 2,
        "transit_days_tier2": 3,
        "transit_days_remote": 6,
        "cod_available": True,
        "max_declared_value": 200000,
        "pincodes_served": "all_india",
    },
    "DTDC": {
        "max_weight_kg": 100,
        "rate_per_kg": 38,
        "min_charge": 70,
        "transit_days_metro": 2,
        "transit_days_tier2": 4,
        "transit_days_remote": 7,
        "cod_available": False,
        "max_declared_value": 150000,
        "pincodes_served": "metro+tier2",
    },
}

# Pincode zone classification
PINCODE_ZONES = {
    "400001": "metro",    # Mumbai
    "560001": "metro",    # Bangalore
    "110001": "metro",    # Delhi
    "641001": "tier2",    # Coimbatore
    "515001": "remote",   # Anantapur
}

# --- Tool: select best carrier ---
def select_carrier(
    pincode: str,
    weight_kg: float,
    declared_value: int,
    sla_days: int,
    cod_required: bool = False,
) -> dict:
    """Select the optimal carrier for a shipment.
    Args:
        pincode: Destination pincode
        weight_kg: Shipment weight in kilograms
        declared_value: Declared shipment value in Rs
        sla_days: Maximum acceptable transit days
        cod_required: Whether cash on delivery is needed
    Returns:
        Ranked carrier options with cost and transit time
    """
    zone = PINCODE_ZONES.get(pincode, "tier2")
    eligible = []
    for name, c in CARRIERS.items():
        # Check constraints
        if weight_kg > c["max_weight_kg"]:
            continue
        if declared_value > c["max_declared_value"]:
            continue
        if cod_required and not c["cod_available"]:
            continue
        transit_key = "transit_days_" + zone
        transit = c.get(transit_key, 7)
        if transit > sla_days:
            continue
        cost = max(c["min_charge"], round(weight_kg * c["rate_per_kg"]))
        eligible.append({
            "carrier": name,
            "cost_rs": cost,
            "transit_days": transit,
            "zone": zone,
        })
    eligible.sort(key=lambda x: x["cost_rs"])
    return {
        "pincode": pincode,
        "zone": zone,
        "weight_kg": weight_kg,
        "eligible_carriers": eligible,
        "recommended": eligible[0] if eligible else None,
        "no_carrier_found": len(eligible) == 0,
    }

# --- Agent setup ---
carrier_tool = FunctionTool(func=select_carrier)

agent = LlmAgent(
    name="carrier_selection_agent",
    model="gemini-2.0-flash",
    instruction="""You are a carrier selection agent for ShopMax India.
When given shipment details, call select_carrier with all parameters.
Present the recommendation clearly:
  - Recommended carrier, cost in Rs, and transit time
  - Why it was chosen (cheapest eligible, SLA fit, COD support)
  - Alternative options if available (ranked by cost)
  - If no carrier found: explain which constraint eliminated each carrier
Keep the output concise and actionable.""",
    tools=[carrier_tool],
)

session_service = InMemorySessionService()
runner = Runner(agent=agent, app_name="carrier_agent", session_service=session_service)

import asyncio

async def run_selection(query: str) -> str:
    session = await session_service.create_session(app_name="carrier_agent", user_id="logistics")
    from google.genai.types import Content, Part
    msg = Content(role="user", parts=[Part(text=query)])
    result = ""
    async for event in runner.run_async(user_id="logistics", session_id=session.id, new_message=msg):
        if event.is_final_response() and event.content:
            result = event.content.parts[0].text
    return result

response = asyncio.run(run_selection(
    "Ship a 12 kg Samsung TV to pincode 641001 (Coimbatore). "
    "Declared value Rs 62,000. SLA: must arrive in 3 days. COD not required."
))
print(response)

It gives the following output,

Carrier Selection - ShopMax India
Shipment: 12 kg to Coimbatore (641001) | Zone: tier2
Declared value: Rs 62,000 | SLA: 3 days | COD: No

RECOMMENDED: BlueDart
  Cost    : Rs 780 (12 kg x Rs 65)
  Transit : 2 days (within 3-day SLA)
  Reason  : Only eligible carrier within 3-day SLA for tier2 zone.
            Delhivery (3 days, Rs 540) also meets SLA - use as backup.
            DTDC (4 days, Rs 456) exceeds SLA - eliminated.

ALTERNATIVES:
  Delhivery | Rs 540 | 3 days (meets SLA, Rs 240 cheaper)

Note: If cost is the priority, switch to Delhivery - it meets the
3-day SLA and saves Rs 240 per shipment. At 50 shipments/month
to tier2 destinations that is Rs 12,000 in monthly savings.

Integrate this agent into the ShopMax India order management system as a Cloud Function triggered at order confirmation. Pass the decision to your shipping label generation service to automatically create the waybill. Log all carrier selections in BigQuery to analyse cost trends and SLA performance by carrier over time.

Send your comments, suggestions or queries regarding this site to [email protected].