# Streaming, Push Notifications and Security in A2A — MCP & Agent-to-Agent Protocols

Source: https://www.geekswithgeeks.com/en/mcp-a2a/a-streaming-auth

> Handle long tasks and protect cross-organisation calls.

## Long tasks and trust boundaries

For short work the client can wait for a response. For longer work A2A offers **streaming** (the client receives incremental status and artifact updates, typically over Server-Sent Events) and **push notifications** (the remote agent calls a webhook the client supplied when the task changes state, so the client need not keep a connection open). Messages travel over standard web transports such as **JSON-RPC over HTTPS**, and later spec versions also describe other bindings. Because calls cross **organisational boundaries**, use **TLS**, authenticate with the schemes the Agent Card declares (for example OAuth 2.0 bearer tokens or API keys), **authorise** per skill and per data type, **validate webhook calls** (signatures or tokens), rate-limit, and log every delegation. Treat remote-agent output like tool output: **untrusted data** that may contain injected instructions.

## Share the minimum

Send a remote agent a redacted summary, not your whole customer record. It is outside your trust boundary.

**Quiz:** What is the purpose of push notifications in A2A?

- [ ] Encrypt cards
- [ ] Send ads to users
- [x] Notify the client of task updates without holding a connection open
- [ ] Replace the task id

*Answer:* Notify the client of task updates without holding a connection open. A webhook callback suits tasks that take minutes or longer.