---
title: "Formations"
description: "While an agent session is active, the runtime serves a small HTTP endpoint exposing an Agent Card (/.well-known/agent-card.json) and a JSON-RPC 2.0 task interface, so other capsules or agents can discover the capsule…"
canonical_url: "https://docs.murmur.nexus/concepts/formations"
last_updated: "2026-08-12T13:32:17.000Z"
---

# Formations

> **Partially implemented**
>
> Formations are an area of Murmur that is only partly built out. Agent Card discovery and
> A2A messaging between capsules, described below, are live today.

## Agent Card & A2A messaging

While an agent session is active, the runtime serves a small HTTP endpoint exposing an Agent
Card (`/.well-known/agent-card.json`) and a JSON-RPC 2.0 task interface, so other capsules or
agents can discover the capsule and hand it a task. An incoming message reserves an active
task slot (`Empty` → `Running` → `Done`); acceptance depends on the capsule's
`lifecycle.task_acceptance` setting (see [Capsule
lifecycle](/concepts/session-loop.md#capsule-lifecycle)). See [Connect two capsules with A2A
messaging](/how-to/capsules-a2a-messaging.md) for the full protocol and examples.