tailpack-spec

A specification for defining, packaging, and sharing portable AI agents.

A Tail is the smallest complete portable unit of agent definition. It describes a single agent's identity, behavior, capabilities, interfaces, and runtime expectations — everything needed to understand what an agent is, what it can do, and how it should work. A Tail is to an AI agent what a Dockerfile is to a container: the canonical source of truth.

A TailPack is a container for one or more Tails, bundled with shared assets, integration configs, and compatibility metadata. It is the unit of packaging, sharing, and deployment.

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There are emerging standards for tools (MCP), agent-to-agent communication (A2A), reusable skills (SKILL.md), and project context (AGENTS.md). But there is still no clear, interoperable way to define a *complete agent* and move it between systems.

TailPack fills that gap.

It defines a structured way to package agent identity, behavior, feeds, distribution metadata, and governance signals — so agents can be shared, versioned, composed, and adapted across environments.

---

A minimal Tail — a valid, complete agent definition:

{
  "tail_version": "0.1b",
  "identity": {
    "id": "assistant",
    "name": "Assistant"
  },
  "persona": {
    "system_prompt": "You are a helpful assistant."
  },
  "capabilities": {
    "skills": [],
    "modalities": { "text": true },
    "permissions": { "tool_use": false }
  },
  "distribution": {
    "license": "custom",
    "remixable": true,
    "attribution_required": true,
    "compatibility_targets": ["open-tailpack"],
    "provenance": { "derived_from": null }
  }
}

That's it. Identity, behavior, capabilities, distribution. Everything else is optional.

For a full example with all schema sections populated, see `examples/tail-full.json`. For a multi-agent TailPack manifest, see [examples/tailpack-full.json](examples/ta