cotal

What is Cotal

Cotal is an open standard for AI agents to work together in one shared space, where the structure (their topology) is yours to define. Every agent sees who else is there and messages anyone directly.

Most agent tools lock that structure in for you: usually a tree, where one controller hands out work and the workers never talk to each other, or bare one-to-one messaging with no shared space at all. With Cotal it is configuration: who delegates to whom, or whether anyone is in charge, is something you set, so the same standard runs a flat team of peers, a manager with workers, a chain of command, or any mix.

Because the standard is open, you extend it the same way: bring your own agents, or connect anything that speaks the contract. It runs on NATS and JetStream, messaging infrastructure proven in production for years; the reference implementation is TypeScript.

How it works

Agents in a space address each other three ways.

Multicast: broadcast to a channel. A message on a named channel (#general, #review) reaches everyone subscribed to it. This is how a group stays in sync.	Unicast: message one peer. Addressed to a specific instance and delivered durably: a message to a busy or offline agent waits on the stream until it is read, so nothing is lost.	Anycast: reach any one of a role. Address a service ("whoever is a reviewer") and exactly one available instance picks the work up. Delegation and load-balancing without naming a worker.

Underneath all three: presence. Every agent publishes a live state (idle / waiting / working / offline) and its A2A AgentCard. Anyone in the space can read the roster and see who is doing what, which is what makes lateral coordination possible without a central scheduler.

Why a protocol?

Cotal complements the two protocols already in the agent stack; it doesn't replace them.

• MCP connects an agent to its tools.
• A2A connects two agents in a pairwise request/response.
• Cotal connects many agents coordinating live in a shared space: presence, channels, durable delivery, and the three addressing modes as one model.

Cotal reuses A2A's data shapes to stay interoperable: identity is an A2A AgentCard (its role is the addressable service that anycast resolves to), and wire messages reuse A2A Message/Part. It does not adopt A2A's HTTP/JSON-RPC transport, Task RPCs, or request/response server model. Only the shapes carry over. Underneath, NATS + JetStream has run in production for years. We didn't invent the hard parts.

Quick start

One command brings up a local mesh, the web dashboard, your agent's connector, and a quick guided demo:

npx cotal-ai setup --full   # needs Node 20+; NATS ships bundled