Protocol - Aflux

Aflux implements MCP revision 2026-07-28. It is not backwards compatible with the revisions before it, and most of what it removed is what a reader coming from an older MCP server will look for and not find.

What is gone

Removed	Detail
The `initialize` handshake	No `initialize` / `notifications/initialized`. Every request stands alone and carries its own protocol version, client identity and capabilities in `_meta`.
Protocol sessions	No `Mcp-Session-Id`. An incoming one is ignored; we never mint one.
The GET stream	`GET /mcp` and `DELETE /mcp` answer `405`, not `401` — an older client is asking for something that no longer exists, and that is the honest answer.
SSE resumability	`Last-Event-ID` is ignored.
`roots`, `sampling`, `logging`	Deprecated in the revision; not implemented.

What is new

server/discover
The MCP-Protocol-Version, Mcp-Method and Mcp-Name headers, validated against the body — any disagreement is -32020.
resultType on every result.
ttlMs and cacheScope on cacheable list results.

Two kinds of failure

Putting a failure in the wrong one is the easiest mistake to make against this server, and the distinction is deliberate:

Protocol errors

Malformed JSON-RPC, a bad header, an unknown method, an unknown tool. Travel as a JSON-RPC error.The client is expected to fix these. A model usually cannot.

Tool execution errors

A project that is not there, a malformed date, an exhausted balance. Travel as a normal result with isError: true.The client hands these to the model — the sentence explaining what went wrong is what lets it retry correctly.

Authentication is the one case that is neither: a request with no valid key is a plain HTTP 401, not a JSON-RPC error and not a tool failure.

Browser origins

/mcp is meant for desktop clients, which send no Origin header at all — that is the normal case and it is allowed. An Origin that is present and is not on the server’s allow-list is refused with 403, per the DNS-rebinding rule. If you need a browser origin allowed, ask support.

A minimal call

curl -X POST https://backend.aflux.ai/mcp \
  -H "Authorization: Bearer $AFLUX_KEY" \
  -H "Content-Type: application/json" \
  -H "MCP-Protocol-Version: 2026-07-28" \
  -H "Mcp-Method: tools/list" \
  -d '{"jsonrpc":"2.0","id":1,"method":"tools/list"}'

The Mcp-Method header must agree with the method in the body. Disagreement is -32020.

​What is gone

​What is new

​Two kinds of failure