https://www.youtube.com/watch?v=rwSpX2M5S1Q&t=3947s

This sample demonstrates a currency conversion agent built with LangGraph and exposed through the A2A protocol. It showcases conversational interactions with support for multi-turn dialogue and streaming responses.

How It Works
This agent uses LangGraph with LLM (for example Google Gemini..) to provide currency exchange information through a ReAct agent pattern. The A2A protocol enables standardized interaction with the agent, allowing clients to send requests and receive real-time updates.

Key Features
Multi-turn Conversations: Agent can request additional information when needed
Real-time Streaming: Provides status updates during processing
Push Notifications: Support for webhook-based notifications
Conversational Memory: Maintains context across interactions
Currency Exchange Tool: Integrates with Frankfurter API for real-time rates
Prerequisites
Python 3.12 or higher
UV
Access to an LLM and API Key
Setup & Running
Navigate to the samples directory:

cd samples/python/agents/langgraph
Create an environment file with your API key:

If you're using a Google Gemini model (gemini-pro, etc.):
echo "GOOGLE_API_KEY=your_api_key_here" > .env

If you're using OpenAI or any compatible API (e.g., local LLM via Ollama, LM Studio, etc.):

echo "API_KEY=your_api_key_here" > .env (not neccessary if have no api key)
echo "TOOL_LLM_URL=your_llm_url" > .env
echo "TOOL_LLM_NAME=your_llm_name" > .env
Run the agent:

Basic run on default port 10000

uv run app

On custom host/port

uv run app --host 0.0.0.0 --port 8080
In a separate terminal, run the test client:

uv run app/test_client.py
Build Container Image
Agent can also be built using a container file.

Navigate to the samples/python/agents/langgraph directory:
cd samples/python/agents/langgraph
Build the container file

podman build . -t langgraph-a2a-server
Tip

Podman is a drop-in replacement for docker which can also be used in these commands.

Run your container

podman run -p 10000

-e GOOGLE_API_KEY=your_api_key_here langgraph-a2a-server
Run A2A client (follow step 5 from the section above)

Important

Access URL: You must access the A2A client through the URL 0.0.0.0

. Using localhost will not work.
Hostname Override: If you're deploying to an environment where the hostname is defined differently outside the container, use the HOST_OVERRIDE environment variable to set the expected hostname on the Agent Card. This ensures proper communication with your client application.
Technical Implementation
LangGraph ReAct Agent: Uses the ReAct pattern for reasoning and tool usage
Streaming Support: Provides incremental updates during processing
Checkpoint Memory: Maintains conversation state between turns
Push Notification System: Webhook-based updates with JWK authentication
A2A Protocol Integration: Full compliance with A2A specifications
Limitations
Only supports text-based input/output (no multi-modal support)
Uses Frankfurter API which has limited currency options
Memory is session-based and not persisted between server restarts
Examples
Synchronous request

Request:

POST http://localhost:10000
Content-Type: application/json

{
"id": "12113c25-b752-473f-977e-c9ad33cf4f56",
"jsonrpc": "2.0",
"method": "message/send",
"params": {
"message": {
"kind": "message",
"messageId": "120ec73f93024993becf954d03a672bc",
"parts": [
{
"kind": "text",
"text": "how much is 10 USD in INR?"
}
],
"role": "user"
}
}
}
Response:

{
"id": "12113c25-b752-473f-977e-c9ad33cf4f56",
"jsonrpc": "2.0",
"result": {
"artifacts": [
{
"artifactId": "08373241-a745-4abe-a78b-9ca60882bcc6",
"name": "conversion_result",
"parts": [
{
"kind": "text",
"text": "10 USD is 856.2 INR."
}
]
}
],
"contextId": "e329f200-eaf4-4ae9-a8ef-a33cf9485367",
"history": [
{
"contextId": "e329f200-eaf4-4ae9-a8ef-a33cf9485367",
"kind": "message",
"messageId": "120ec73f93024993becf954d03a672bc",
"parts": [
{
"kind": "text",
"text": "how much is 10 USD in INR?"
}
],
"role": "user",
"taskId": "58124b63-dd3b-46b8-bf1d-1cc1aefd1c8f"
},
{
"contextId": "e329f200-eaf4-4ae9-a8ef-a33cf9485367",
"kind": "message",
"messageId": "d8b4d7de-709f-40f7-ae0c-fd6ee398a2bf",
"parts": [
{
"kind": "text",
"text": "Looking up the exchange rates..."
}
],
"role": "agent",
"taskId": "58124b63-dd3b-46b8-bf1d-1cc1aefd1c8f"
},
{
"contextId": "e329f200-eaf4-4ae9-a8ef-a33cf9485367",
"kind": "message",
"messageId": "ee0cb3b6-c3d6-4316-8d58-315c437a2a77",
"parts": [
{
"kind": "text",
"text": "Processing the exchange rates.."
}
],
"role": "agent",
"taskId": "58124b63-dd3b-46b8-bf1d-1cc1aefd1c8f"
}
],
"id": "58124b63-dd3b-46b8-bf1d-1cc1aefd1c8f",
"kind": "task",
"status": {
"state": "completed"
}
}
}
Multi-turn example

Request - Seq 1:

POST http://localhost:10000
Content-Type: application/json

{
"id": "27be771b-708f-43b8-8366-968966d07ec0",
"jsonrpc": "2.0",
"method": "message/send",
"params": {
"message": {
"kind": "message",
"messageId": "296eafc9233142bd98279e4055165f12",
"parts": [
{
"kind": "text",
"text": "How much is the exchange rate for 1 USD?"
}
],
"role": "user"
}
}
}
Response - Seq 2:

{
"id": "27be771b-708f-43b8-8366-968966d07ec0",
"jsonrpc": "2.0",
"result": {
"contextId": "a7cc0bef-17b5-41fc-9379-40b99f46a101",
"history": [
{
"contextId": "a7cc0bef-17b5-41fc-9379-40b99f46a101",
"kind": "message",
"messageId": "296eafc9233142bd98279e4055165f12",
"parts": [
{
"kind": "text",
"text": "How much is the exchange rate for 1 USD?"
}
],
"role": "user",
"taskId": "9d94c2d4-06e4-40e1-876b-22f5a2666e61"
}
],
"id": "9d94c2d4-06e4-40e1-876b-22f5a2666e61",
"kind": "task",
"status": {
"message": {
"contextId": "a7cc0bef-17b5-41fc-9379-40b99f46a101",
"kind": "message",
"messageId": "f0f5f3ff-335c-4e77-9b4a-01ff3908e7be",
"parts": [
{
"kind": "text",
"text": "Please specify which currency you would like to convert to."
}
],
"role": "agent",
"taskId": "9d94c2d4-06e4-40e1-876b-22f5a2666e61"
},
"state": "input-required"
}
}
}
Request - Seq 3:

POST http://localhost:10000
Content-Type: application/json

{
"id": "b88d818d-1192-42be-b4eb-3ee6b96a7e35",
"jsonrpc": "2.0",
"method": "message/send",
"params": {
"message": {
"contextId": "a7cc0bef-17b5-41fc-9379-40b99f46a101",
"kind": "message",
"messageId": "70371e1f231f4597b65ccdf534930ca9",
"parts": [
{
"kind": "text",
"text": "CAD"
}
],
"role": "user",
"taskId": "9d94c2d4-06e4-40e1-876b-22f5a2666e61"
}
}
}
Response - Seq 4:

{
"id": "b88d818d-1192-42be-b4eb-3ee6b96a7e35",
"jsonrpc": "2.0",
"result": {
"artifacts": [
{
"artifactId": "08373241-a745-4abe-a78b-9ca60882bcc6",
"name": "conversion_result",
"parts": [
{
"kind": "text",
"text": "The exchange rate for 1 USD to CAD is 1.3739."
}
]
}
],
"contextId": "a7cc0bef-17b5-41fc-9379-40b99f46a101",
"history": [
{
"contextId": "a7cc0bef-17b5-41fc-9379-40b99f46a101",
"kind": "message",
"messageId": "296eafc9233142bd98279e4055165f12",
"parts": [
{
"kind": "text",
"text": "How much is the exchange rate for 1 USD?"
}
],
"role": "user",
"taskId": "9d94c2d4-06e4-40e1-876b-22f5a2666e61"
},
{
"contextId": "a7cc0bef-17b5-41fc-9379-40b99f46a101",
"kind": "message",
"messageId": "f0f5f3ff-335c-4e77-9b4a-01ff3908e7be",
"parts": [
{
"kind": "text",
"text": "Please specify which currency you would like to convert to."
}
],
"role": "agent",
"taskId": "9d94c2d4-06e4-40e1-876b-22f5a2666e61"
},
{
"contextId": "a7cc0bef-17b5-41fc-9379-40b99f46a101",
"kind": "message",
"messageId": "70371e1f231f4597b65ccdf534930ca9",
"parts": [
{
"kind": "text",
"text": "CAD"
}
],
"role": "user",
"taskId": "9d94c2d4-06e4-40e1-876b-22f5a2666e61"
},
{
"contextId": "a7cc0bef-17b5-41fc-9379-40b99f46a101",
"kind": "message",
"messageId": "0eb4f200-a8cd-4d34-94f8-4d223eb1b2c0",
"parts": [
{
"kind": "text",
"text": "Looking up the exchange rates..."
}
],
"role": "agent",
"taskId": "9d94c2d4-06e4-40e1-876b-22f5a2666e61"
},
{
"contextId": "a7cc0bef-17b5-41fc-9379-40b99f46a101",
"kind": "message",
"messageId": "41c7c03a-a772-4dc8-a868-e8c7b7defc91",
"parts": [
{
"kind": "text",
"text": "Processing the exchange rates.."
}
],
"role": "agent",
"taskId": "9d94c2d4-06e4-40e1-876b-22f5a2666e61"
}
],
"id": "9d94c2d4-06e4-40e1-876b-22f5a2666e61",
"kind": "task",
"status": {
"state": "completed"
}
}
}
Streaming example

Request:

{
"id": "6d12d159-ec67-46e6-8d43-18480ce7f6ca",
"jsonrpc": "2.0",
"method": "message/stream",
"params": {
"message": {
"kind": "message",
"messageId": "2f9538ef0984471aa0d5179ce3c67a28",
"parts": [
{
"kind": "text",
"text": "how much is 10 USD in INR?"
}
],
"role": "user"
}
}
}
Response:

data: {"id":"6d12d159-ec67-46e6-8d43-18480ce7f6ca","jsonrpc":"2.0","result":{"contextId":"cd09e369-340a-4563-bca4-e5f2e0b9ff81","history":[{"contextId":"cd09e369-340a-4563-bca4-e5f2e0b9ff81","kind":"message","messageId":"2f9538ef0984471aa0d5179ce3c67a28","parts":[{"kind":"text","text":"how much is 10 USD in INR?"}],"role":"user","taskId":"423a2569-f272-4d75-a4d1-cdc6682188e5"}],"id":"423a2569-f272-4d75-a4d1-cdc6682188e5","kind":"task","status":{"state":"submitted"}}}

data: {"id":"6d12d159-ec67-46e6-8d43-18480ce7f6ca","jsonrpc":"2.0","result":{"contextId":"cd09e369-340a-4563-bca4-e5f2e0b9ff81","final"

,"kind":"status-update","status":{"message":{"contextId":"cd09e369-340a-4563-bca4-e5f2e0b9ff81","kind":"message","messageId":"1854a825-c64f-4f30-96f2-c8aa558b83f9","parts":[{"kind":"text","text":"Looking up the exchange rates..."}],"role":"agent","taskId":"423a2569-f272-4d75-a4d1-cdc6682188e5"},"state":"working"},"taskId":"423a2569-f272-4d75-a4d1-cdc6682188e5"}}

data: {"id":"6d12d159-ec67-46e6-8d43-18480ce7f6ca","jsonrpc":"2.0","result":{"contextId":"cd09e369-340a-4563-bca4-e5f2e0b9ff81","final"

,"kind":"status-update","status":{"message":{"contextId":"cd09e369-340a-4563-bca4-e5f2e0b9ff81","kind":"message","messageId":"e72127a6-4830-4320-bf23-235ac79b9a13","parts":[{"kind":"text","text":"Processing the exchange rates.."}],"role":"agent","taskId":"423a2569-f272-4d75-a4d1-cdc6682188e5"},"state":"working"},"taskId":"423a2569-f272-4d75-a4d1-cdc6682188e5"}}

data: {"id":"6d12d159-ec67-46e6-8d43-18480ce7f6ca","jsonrpc":"2.0","result":{"artifact":{"artifactId":"08373241-a745-4abe-a78b-9ca60882bcc6","name":"conversion_result","parts":[{"kind":"text","text":"10 USD is 856.2 INR."}]},"contextId":"cd09e369-340a-4563-bca4-e5f2e0b9ff81","kind":"artifact-update","taskId":"423a2569-f272-4d75-a4d1-cdc6682188e5"}}

data: {"id":"6d12d159-ec67-46e6-8d43-18480ce7f6ca","jsonrpc":"2.0","result":{"contextId":"cd09e369-340a-4563-bca4-e5f2e0b9ff81","final"

,"kind":"status-update","status":{"state":"completed"},"taskId":"423a2569-f272-4d75-a4d1-cdc6682188e5"}}