Analysis
Comparison Analysis
How A2UI relates to and differs from existing approaches.
Capability Matrix
| Capability | JSON Mode | Function Calling | MCP | A2UI |
|---|---|---|---|---|
| Structured output | ||||
| Schema validation | ||||
| UI primitives defined | ||||
| Renderer-agnostic | ||||
| Model-agnostic | ||||
| Interoperability standard | ||||
| Streaming support | ||||
| Visual layout hints |
Supported
Partial
Not supported
Key Differentiators
vs
JSON Mode
JSON mode provides structure but no semantics. A2UI defines what the structure means and how it should be rendered. An A2UI intent is a specific vocabulary; raw JSON is just syntax.
vs
Function Calling
Function calling is action-oriented (do something). A2UI is presentation-oriented (show something). They're complementary: an agent might call a function to get data, then emit an A2UI intent to display it.
vs
MCP
MCP defines the protocol layer (how agents discover and invoke capabilities). A2UI defines the presentation layer (how results are displayed). They work together: MCP tools could return A2UI intents as their output format.
Integration Opportunities
A2UI intents can be used as MCP tool return values
Function calling schemas can include A2UI primitives as output types
JSON mode can use A2UI schemas for structured output
Existing UIs can adopt A2UI incrementally, one primitive at a time