Route.mcp() needed to register routes correctly with Ktor

[ukarlsson]

Describe the bug
There is no Route.mcp() method, and this causes issues since Routing.mcp() seems to register the route on the top-level instead of the route where I need it. It seems like the example in the README.md is broken since that registers on the top-level instead of the route.

I had to add this locally to make it work

@KtorDsl
fun Route.mcp(block: () -> Server) {
  val transports = ConcurrentMap<String, SseServerTransport>()

  sse { mcpSseEndpoint("", transports, block) }

  post { mcpPostEndpoint(transports) }
}

Now with this I can actually use it as intended

      route("/mcp") {
        authenticate("mcp-bearer") { mcp { mcpServer } }
      }

But with the Routing.mcp() it did not get registered in the right location. I also had to copy over util methods below to make it work since these we internal

suspend fun ServerSSESession.mcpSseEndpoint
internal fun ServerSSESession.mcpSseTransport
suspend fun RoutingContext.mcpPostEndpoint(transports: ConcurrentMap<String, SseServerTransport>)

Many thanks

[konrader]

We ran into the same problem.
This basically stops you from register MCP endpoints on any subpath and only have it served from root.

[wrimle]

It seems to me that this is a regression from renaming Application.MCP to Application.mcp. The compiler is not able to handle that Application.mcp and Route.mcp has the same name

[johannesrave]

i've been spending a few hours on this as well, just noticed my server is always available at root regardless of the path i specify :/ i think it' the empty string instead of the actual path here?

kotlin-sdk/kotlin-sdk-server/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/server/KtorServer.kt

Line 54 in cae9130

mcpSseEndpoint("", sseTransportManager, block)

that basically leads into SseServerTransport which renders the endpoint when starting the session - i'm a bit unsure. if this was a regression, there probably should be a test that tries to connect to an mcp server at a nested route.