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A2AL Docs

Let Others Call You

This is the other end of the request–response channel: bind a service running on your machine to your AID — a local LLM, an internal API, an automation script. Once bound, other agents or people can call it by address, with no port to open, no domain name and no public IP.

Typical uses: hand a local model service to a colleague or another agent to call; expose an existing internal endpoint to selected peers by AID instead of to the internet.

Bind in three steps

Section titled “Bind in three steps”
Terminal window
a2al register                                   # 1. create an identity (skip if you have one)
a2al inbound bind --addr 127.0.0.1:8080         # 2. bind your local service (use the port it actually listens on)
a2al publish lang.translate --name "Translation" --brief "Chinese ⇄ English"   # 3. publish a service name (optional)

Give --addr the address the service actually listens on. 2121 is a2ald’s API port and cannot be used for binding.

Step 3 is for public lookup: if you hand the AID only to selected peers, you can skip it.

How the other side calls you

Section titled “How the other side calls you”
Terminal window
a2al get <your-AID> /your/api/path      # AID known: call it directly
a2al search lang.translate              # AID unknown: look it up by service name

Expected result

Section titled “Expected result”

The caller runs a2al get <your-AID> /.well-known/agent.json and gets back the JSON your service returns. The caller’s IP, network and NAT setup make no difference.

Keeping the service available

Section titled “Keeping the service available”
  • The binding travels with the identity: bindings are kept in a2ald’s data directory and are restored automatically after a restart from the same directory.
  • Publish records expire: once a2ald stops running, published records expire after about 1 hour and lookups stop matching — for something that must stay findable, keep the daemon resident (on Windows / macOS: a2ald service install; on Linux, see the deployment guides).
  • Access control: use an ACL when you need to restrict who may call. Being discoverable is not the same as being callable.
Section titled “Related pages”
GoalPage
Call the other side’s serviceConnect by AID
TCP connections that need to stay upTunnel
Which of the five channels fits which situationChoose the Right Channel