Content
# How It Works
This agent uses **LangGraph** with **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 3.13 or higher
- UV
- Access to an LLM and API Key
## Setup & Running
Navigate to the samples directory:
```bash
cd samples/python/agents/langgraph
```
Create an environment file with your API key:
```bash
echo "GOOGLE_API_KEY=your_api_key_here" > .env
```
Run the agent:
```bash
# Basic run on default port 10000
uv run .
# On custom host/port
uv run . --host 0.0.0.0 --port 8080
```
In a separate terminal, run an A2A client:
```bash
uv run hosts/cli
```
## 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**
```json
POST http://localhost:10000
Content-Type: application/json
{
"jsonrpc": "2.0",
"id": 11,
"method": "tasks/send",
"params": {
"id": "129",
"sessionId": "8f01f3d172cd4396a0e535ae8aec6687",
"acceptedOutputModes": ["text"],
"message": {
"role": "user",
"parts": [
{
"type": "text",
"text": "How much is the exchange rate for 1 USD to INR?"
}
]
}
}
}
```
**Response**
```json
{
"jsonrpc": "2.0",
"id": 11,
"result": {
"id": "129",
"status": {
"state": "completed",
"timestamp": "2025-04-02T16:53:29.301828"
},
"artifacts": [
{
"parts": [
{
"type": "text",
"text": "The exchange rate for 1 USD to INR is 85.49."
}
],
"index": 0
}
],
"history": []
}
}
```
### Multi-turn Example
**Request - Seq 1**
```json
POST http://localhost:10000
Content-Type: application/json
{
"jsonrpc": "2.0",
"id": 10,
"method": "tasks/send",
"params": {
"id": "130",
"sessionId": "a9bb617f2cd94bd585da0f88ce2ddba2",
"acceptedOutputModes": ["text"],
"message": {
"role": "user",
"parts": [
{
"type": "text",
"text": "How much is the exchange rate for 1 USD?"
}
]
}
}
}
```
**Response - Seq 2**
```json
{
"jsonrpc": "2.0",
"id": 10,
"result": {
"id": "130",
"status": {
"state": "input-required",
"message": {
"role": "agent",
"parts": [
{
"type": "text",
"text": "Which currency do you want to convert to? Also, do you want the latest exchange rate or a specific date?"
}
]
},
"timestamp": "2025-04-02T16:57:02.336787"
},
"history": []
}
}
```
**Request - Seq 3**
```json
POST http://localhost:10000
Content-Type: application/json
{
"jsonrpc": "2.0",
"id": 10,
"method": "tasks/send",
"params": {
"id": "130",
"sessionId": "a9bb617f2cd94bd585da0f88ce2ddba2",
"acceptedOutputModes": ["text"],
"message": {
"role": "user",
"parts": [
{
"type": "text",
"text": "CAD"
}
]
}
}
}
```
**Response - Seq 4**
```json
{
"jsonrpc": "2.0",
"id": 10,
"result": {
"id": "130",
"status": {
"state": "completed",
"timestamp": "2025-04-02T16:57:40.033328"
},
"artifacts": [
{
"parts": [
{
"type": "text",
"text": "The current exchange rate is 1 USD = 1.4328 CAD."
}
],
"index": 0
}
],
"history": []
}
}
```
### Streaming Example
**Request**
```json
{
"jsonrpc": "2.0",
"id": 12,
"method": "tasks/sendSubscribe",
"params": {
"id": "131",
"sessionId": "cebd704d0ddd4e8aa646aeb123d60614",
"acceptedOutputModes": ["text"],
"message": {
"role": "user",
"parts": [
{
"type": "text",
"text": "How much is 100 USD in GBP?"
}
]
}
}
}
```
**Response**
```json
data: {"jsonrpc":"2.0","id":12,"result":{"id":"131","status":{"state":"working","message":{"role":"agent","parts":[{"type":"text","text":"Looking up the exchange rates..."}]},"timestamp":"2025-04-02T16:59:34.578939"},"final":false}}
data: {"jsonrpc":"2.0","id":12,"result":{"id":"131","status":{"state":"working","message":{"role":"agent","parts":[{"type":"text","text":"Processing the exchange rates.."}]},"timestamp":"2025-04-02T16:59:34.737052"},"final":false}}
data: {"jsonrpc":"2.0","id":12,"result":{"id":"131","artifact":{"parts":[{"type":"text","text":"Based on the current exchange rate, 1 USD is equivalent to 0.77252 GBP. Therefore, 100 USD would be approximately 77.252 GBP."}],"index":0,"append":false}}}
data: {"jsonrpc":"2.0","id":12,"result":{"id":"131","status":{"state":"completed","timestamp":"2025-04-02T16:59:35.331844"},"final":true}}
```
