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Registry

The Registry is the discovery and coordination layer of Protolink.
It allows agents to register themselves, discover other agents, and interact autonomously over a shared transport.

At a high level:

  • Agents announce their existence to a Registry
  • Other agents can discover agents dynamically
  • The Registry runs as a server and exposes a transport-backed API
  • Agents can operate autonomously, without manual function calls

Why a Registry?

The Registry enables dynamic, decentralized agent systems.
Agents don’t need hard-coded references to each other — they discover peers at runtime and coordinate through messages.

Inspiration

The Registry is inspired by Google's A2A paper, which introduces a similar concept for agent-to-agent discovery.

Core Concepts

Registry

The Registry is a long-running service responsible for:

  • Tracking active agents
  • Storing their AgentCard metadata
  • Exposing discovery endpoints via a transport
  • Acting as the entry point for multi-agent systems

The Registry does not execute agent logic.
It only provides discovery, metadata, and routing primitives.

Agent Registration

Each agent registers itself by sending its AgentCard to the Registry when it starts.

An AgentCard typically includes:

  • Agent name
  • Description
  • Capabilities / skills
  • Transport URL
  • Optional metadata

Once registered, the agent becomes discoverable by other agents.

Dynamic Systems

Agents may join or leave at any time.
The Registry reflects the current state of the system dynamically.

Agent Discovery

Agents query the Registry to discover other agents.

Discovery supports optional filtering, for example:

  • By name
  • By capability
  • By arbitrary metadata
agents = await registry.discover(filters={
    "capability": "search",
    "domain": "finance"
})

Registry

The Registry is the discovery and coordination layer of Protolink.
It allows agents to register themselves, discover other agents, and interact autonomously over a shared transport.

At a high level:

  • Agents announce their existence to a Registry
  • Other agents can discover agents dynamically
  • The Registry runs as a server and exposes a transport-backed API
  • Agents can operate autonomously, without manual function calls

Why a Registry?

The Registry enables dynamic, decentralized agent systems.
Agents don’t need hard-coded references to each other — they discover peers at runtime and coordinate through messages.

Core Concepts

Registry

The Registry is a long-running service responsible for:

  • Tracking active agents
  • Storing their AgentCard metadata
  • Exposing discovery endpoints via a transport
  • Acting as the entry point for multi-agent systems

The Registry does not execute agent logic.
It only provides discovery, metadata, and routing primitives.

Agent Registration

Each agent registers itself by sending its AgentCard to the Registry when it starts.

An AgentCard typically includes:

  • Agent name
  • Description
  • Capabilities / skills
  • Transport URL
  • Optional metadata

Once registered, the agent becomes discoverable by other agents.

Dynamic Systems

Agents may join or leave at any time.
The Registry reflects the current state of the system dynamically.

Agent Discovery

Agents query the Registry to discover other agents.

Discovery supports optional filtering, for example:

  • By name
  • By capability
  • By arbitrary metadata
agents = await registry.discover(filters={
    "capability": "search",
    "domain": "finance"
})

Filters are Optional

Calling discover() with no filters returns all registered agents.

Transport Integration

The Registry is transport-agnostic. It relies on a Transport implementation to expose its API.

Currently supported:

  • HTTPTransport (via protolink.transport.HTTPTransport)

The transport is responsible for:

  • Binding to a host and port
  • Exposing registry endpoints
  • Handling request/response lifecycle

Starting the Registry

The Registry is started via its transport

from protolink.discovery.registry import Registry
from protolink.transport import HTTPTransport

transport = HTTPTransport(url="http://localhost:9020")
registry = Registry(transport)

await registry.start()

This starts a registry server that agents can connect to.

Single Source of Truth

The Registry’s public URL is derived from the transport and used by agents for registration and discovery.

URL Handling

Both Agents and the Registry expose a url property.

  • The Transport owns host and port
  • The url is a derived, canonical representation

To avoid duplication, transports provide helpers to derive host and port from a URL.

transport = HTTPTransport(url="http://localhost:8000")

This ensures consistent configuration across agents and registry instances.