Content
# Agent2Agent (A2A) Go Library
[](https://godoc.org/github.com/mashiike/a2a)
[](https://goreportcard.com/report/github.com/mashiike/a2a)
[](https://opensource.org/licenses/MIT)
Agent2Agent (A2A) is a Go library implementing an open protocol designed to facilitate communication between agents. This library provides features such as task management, session management, streaming, push notifications, and history tracking to streamline agent-to-agent collaboration.
For more details about the A2A protocol, refer to the [official documentation](https://google.github.io/A2A/#/documentation).
## Installation
Install the library using the following command:
```bash
go get github.com/mashiike/a2a
```
## Usage
### Creating a Server
The following is an example of creating an A2A server:
```go
package main
import (
"context"
"log"
"net/http"
"github.com/mashiike/a2a"
)
func main() {
card := &a2a.AgentCard{
Name: "Example Agent",
URL: "http://localhost:8080",
Version: "1.0.0",
Skills: []a2a.Skill{
{
ID: "example-skill",
Name: "Example Skill",
Tags: []string{"example"},
},
},
}
agent := a2a.AgentFunc(func(ctx context.Context, tr a2a.TaskResponder, task *a2a.Task) error {
log.Printf("Received task: %s", task.ID)
tr.SetStatus(ctx, a2a.TaskStatus{State: a2a.TaskStateWorking}, false, nil)
tr.WriteArtifact(ctx, a2a.Artifact{
Index: 0,
Parts: []a2a.Part{
a2a.TextPart("Hello, this is a response from the server."),
},
}, nil)
tr.SetStatus(ctx, a2a.TaskStatus{State: a2a.TaskStateCompleted}, true, nil)
return nil
})
handler, err := a2a.NewHandler(card, agent, nil)
if err != nil {
log.Fatalf("Failed to create handler: %v", err)
}
log.Println("Starting server on :8080")
http.ListenAndServe(":8080", handler)
}
```
The server functionality can be implemented by registering a struct that satisfies the following `Agent` interface:
```go
type Agent interface {
Invoke(ctx context.Context, r TaskResponder, task *Task) error
}
```
The above example synchronously returns results, but you can also process tasks asynchronously using Go routines. By replacing certain infrastructure implementations, the server can be made more practical. These replacements can be configured using the third argument of `NewHandler`.
For more details, refer to the [godoc](https://pkg.go.dev/github.com/mashiike/a2a#HandlerOptions).
#### Store Interface
The `Store` interface manages tasks and their associated data. If the server operates asynchronously or across multiple server instances, it is recommended to replace the default `InMemoryStore` with a custom implementation.
```go
type Store interface {
GetHistory(ctx context.Context, sessionID string, historyLength int) ([]Message, error)
AppendHistory(ctx context.Context, sessionID string, message Message) error
CreateTask(ctx context.Context, task *Task) error
GetTask(ctx context.Context, taskID string) (*Task, error)
UpdateStatus(ctx context.Context, taskID string, status TaskStatus) error
UpdateArtifact(ctx context.Context, taskID string, artifact Artifact) error
}
```
Additionally, implementing the `PushNotificationStore` interface allows for managing push notifications for tasks.
```go
type PushNotificationStore interface {
CreateTaskPushNotification(ctx context.Context, cfg *TaskPushNotificationConfig) error
GetTaskPushNotification(ctx context.Context, taskID string) (*TaskPushNotificationConfig, error)
}
```
#### PubSub Interface
The `PubSub` interface is required when setting `capabilities.streaming` to `true`.
```go
type PubSub interface {
Publish(ctx context.Context, event StreamingEvent) error
Subscribe(ctx context.Context, taskID string) (<-chan StreamingEvent, error)
}
```
When updating the task state, the `Handler` uses `Publish` to distribute change information if `HandlerOptions.TaskEventQueue` is not `nil`. Additionally, the `tasks/sendSubscribe` and `tasks/resubscribe` RPC methods use `Subscribe` to receive change information.
### Creating a Client
The following is an example of creating a client to communicate with an A2A server:
```go
package main
import (
"context"
"encoding/json"
"log"
"os"
"github.com/google/uuid"
"github.com/mashiike/a2a"
)
func main() {
client, err := a2a.NewClient("http://localhost:8080")
if err != nil {
log.Fatalf("Failed to create client: %v", err)
}
defer client.Close()
params := a2a.TaskSendParams{
ID: uuid.New().String(),
Message: a2a.Message{
Role: a2a.MessageRoleUser,
Parts: []a2a.Part{
a2a.TextPart("Hello, Agent!"),
},
},
}
ctx := context.Background()
task, err := client.SendTask(ctx, params)
if err != nil {
log.Fatalf("Failed to send task: %v", err)
}
enc := json.NewEncoder(os.Stdout)
enc.SetIndent("", " ")
enc.Encode(task)
}
```
## License
This project is licensed under the MIT License. See the [LICENSE](./LICENSE) file for details.
