clientContextProvider - client & server side

[imod]

@Kehrlann following up on modelcontextprotocol/java-sdk#522 (comment) - I managed to inject the customizer on the client side and also see it being called. But I don't see anything being send over the wire and if so, how would I get hold on the context information on the server site? Sorry for the questions...

In my setup, I have a chat calling an mcp server (sse) and the mcp server calling a protected REST server. I do need the auth token to be propagated, but also access to additional context data in the tool.

[Kehrlann]

Hey @imod !

So you need two things:

• The transport context provider in the sync client example
• AND you also need either:
  • A request customizer if you're using spring-ai-starter-mcp-client example ; if you publish it as a bean the spring auto-configuration should pick it up
  • OR an exchange filter if you're using spring-ai-starter-mcp-client-webflux example ; if you publish a WebClient.Builder bean, the Spring auto-config should pick it up

[imod]

@Kehrlann many thanks for this!!! This got to working solution and I only have one thing left...

if I have

chatClient
                .prompt()
                .toolContext(mapOf("customAttr" to "my-custom-value"))
                .advisors { advisor -> advisor.param(ChatMemory.CONVERSATION_ID, conversationId) }
                .user { u -> u.text(question.message) }
                .call()
                .content()

I do see this attribute being send across the wire, but how can I access customAttr in the "Tool" in the MCP server? I tried to inject context: ToolContext in the Tool function, but all context has set is "exchange" (of type McpSyncServerExchange).

[Kehrlann]

I haven't used this myself, but my undertanding is that the Spring MCP client translates tool context to MCP _meta (MCP ref).

You can read the MCP meta on the server side from the McpMeta special parameter.

There should be no need for customization, context, or anything :)

[imod]

many thanks @Kehrlann! McpMeta was the missing part

[Kehrlann]

Glad I could help!