mixed
A2UI
Stream structured generative-interface descriptions to compatible renderers.
- Revision
- 0.9.1 stable / 1.0 candidate
- Authority
- A2UI project
Compatibility layers
Specifications and conventions
These layers coexist. A package format is not a tool protocol; a UI protocol is not an editor-agent transport. Every compatibility claim keeps the specification revision and directional role visible.
Layer map
Interoperability stack
Layer order is explanatory, not a maturity or quality ranking.
- 01Workspace instructions
AGENTS.md and host rules
- 02Reusable capability bundles
Agent Skills
- 03Distribution packages
Agent Plugins and host-native packages
- 04Agent to tools and context
MCP
- 05Website to agent
WebMCP and NLWeb
- 06Agent to interactive UI
MCP Apps, AG-UI, and A2UI
- 07Editor to coding agent
ACP
- 08Session host to clients
AHP
- 09Agent to agent
A2A
open protocol
AG-UI
Stream agent state, events, and interaction between backends and user interfaces.
- Revision
- living
- Authority
- AG-UI community
active
Agent Client Protocol
Connect an editor or client host to an external coding agent.
- Revision
- living
- Authority
- ACP / Zed ecosystem
preview
Agent Host Protocol
Host persistent agent sessions that clients can subscribe to and resume.
- Revision
- 0.5.x
- Authority
- Microsoft
stable
Agent Plugins
Distribute portable agent components in a versioned manifest package.
- Revision
- 1.0.0
- Authority
- Cross-vendor technical steering committee
open standard
Agent Skills
Package reusable instructions with optional references, assets, and scripts.
- Revision
- living
- Authority
- Agent Skills maintainers
stable family
Agent2Agent Protocol
Let agents discover one another and exchange tasks, artifacts, and updates.
- Revision
- 1.0.x
- Authority
- Linux Foundation project
convention
AGENTS.md
Provide repository-scoped instructions to compatible coding agents.
- Revision
- living
- Authority
- Community convention
stable extension
MCP Apps
Return an interactive interface from an MCP tool for rendering inside a compatible host.
- Revision
- 2026-01-26
- Authority
- MCP project
published
Model Context Protocol
Connect hosts and clients to server-provided tools, resources, prompts, and related primitives.
- Revision
- 2026-07-28
- Authority
- MCP project / AAIF ecosystem
early
NLWeb
Expose web content and actions through natural-language-oriented endpoints.
- Revision
- 0.5 TypeSpec
- Authority
- NLWeb community
draft community group report
WebMCP
Let websites expose structured tools to compatible user agents.
- Revision
- 2026-08-26 draft
- Authority
- W3C Web Machine Learning Community Group