> For the complete documentation index, see [llms.txt](https://v2.dataos.info/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://v2.dataos.info/references/interfaces/ai-activation/mcp-layers.md).

# MCP layers

MCP separates message meaning from message transport.

## The two layers

| Layer           | What it handles                                                                                                                           | Example                                                                                                               |
| --------------- | ----------------------------------------------------------------------------------------------------------------------------------------- | --------------------------------------------------------------------------------------------------------------------- |
| Data layer      | The JSON-RPC message model, lifecycle, capability negotiation, requests, responses, notifications, errors, tools, resources, and prompts. | The client sends `tools/call` with arguments for `vulcan_query`. The server returns a structured result or error.     |
| Transport layer | The communication channel that carries MCP messages between the client and server.                                                        | A desktop assistant may connect to a local MCP process. A hosted assistant may connect to Data Product MCP over HTTP. |

The data layer defines what the client and server are saying. The transport layer defines how those messages move.

## Why this separation matters

This split keeps protocol behavior stable across different connection types.

It also lets Data Product MCP support different host environments without changing tool semantics. A local assistant and a hosted assistant can call the same tools and receive the same response shape, even if they connect differently.


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