a2a-agent

A2A Agent Example

Connect to remote A2A (Agent-to-Agent) agents with authentication via the PromptKit SDK.

What You'll Learn

• Builder pattern with NewA2AAgent() for remote agent configuration
• Bearer token authentication with WithAuth()
• Custom headers with WithHeader()
• Skill filtering to expose only specific agent skills
• Retry policies for resilient connections

Prerequisites

• Go 1.21+
• OpenAI API key
• A running A2A agent (this example uses the echo server from examples/a2a-auth-test)

Running the Example

# Terminal 1: Start the echo server
go run ./examples/a2a-auth-test/server

# Terminal 2: Run this example
export OPENAI_API_KEY=your-key
go run .

Code Overview

echoAgent := sdk.NewA2AAgent("http://localhost:9877").
    WithAuth("Bearer", "test-token-123").
    WithHeader("X-Request-Source", "sdk-example").
    WithTimeout(5000).
    WithRetryPolicy(3, 100, 2000).
    WithSkillFilter(&tools.A2ASkillFilter{
        Allowlist: []string{"echo"},
    })

conv, err := sdk.Open("./a2a-agent.pack.json", "assistant",
    sdk.WithA2AAgent(echoAgent),
)

Builder Options

Tool Naming

A2A tools are namespaced as a2a__<agent>__<skill>:

• a2a__echo_agent__echo
• a2a__echo_agent__reverse (blocked by skill filter in this example)

Environment Variables

Key Concepts

1. Auto-Discovery - Agent skills are discovered from the agent card at startup
2. Skill Filtering - Expose only the skills you need
3. Authentication - Bearer, Basic, or custom auth schemes
4. Retry Policy - Exponential backoff for transient failures
5. No Pack Changes - A2A tools don't need to be defined in the pack file

Next Steps

• MCP Tools Example - MCP server integration
• HTTP Transforms Example - Argument transforms and response processing
• Tools Example - Basic tool handling