MCP - quarkus.langchain4j.mcp."client-name".transport-type - Fixed at BuildTime

[KaiSuchomel]

Hey, we are trying to use several mcp Servers in one Ai Service.
Therefore we used (no mcp name given)

@McpToolBox
String useAllMcpServers(@UserMessage String userMessage);

Now we have the issue that the property: quarkus.langchain4j.mcp."client-name".transport-type (see: https://docs.quarkiverse.io/quarkus-langchain4j/dev/mcp.html#quarkus-langchain4j-mcp_section_quarkus-langchain4j-mcp)
must be set at Build-Time, means we must have a dedicated build for every ai service-mcp server combination that we want to use.

Is there a chance that this property must not be set at build and dynamicly detect the mcp servers, so that we only need one Build(Image) and the mcp server can be configured dynamic.

[geoand]

cc @jmartisk

[jmartisk]

I think that we could make the transport-type a runtime property, but I assume that wouldn't solve your problem, because we still need to know the full list of MCP client names at build time (because we register CDI beans for them at build time).

If you need to create MCP clients dynamically at runtime, you can certainly do that (by using the builder of DefaultMcpClient). But these dynamically created MCP clients you will have to manage yourself - they won't get registered as CDI beans, they won't get automatically cleaned up at shutdown,... and they won't be seen by the @McpToolBox annotation - so you will instead have to create a McpToolProvider instance and declare your AI service to use that provider. Basically you would do exactly what is described in the upstream langchain4j documentation: https://docs.langchain4j.dev/tutorials/mcp
with the exception that the correct transport to use for Streamable HTTP would be QuarkusStreamableHttpMcpTransport instead of StreamableHttpMcpTransport and for legacy HTTP/SSE, it is QuarkusHttpMcpTransport instead of HttpMcpTransport

[jmartisk]

Let me know if you need more pointers, we could potentially write some piece of Quarkus-side documentation for this because there will probably be more people needing to create clients dynamically...

[KaiSuchomel]

Thx, for your Answer. I will give it a try and come back when working or not 😄

[KaiSuchomel]

@jmartisk
So far so good. I did manage to get the mcp tool called but the result is not as expected:
Here my Implementation

@ApplicationScoped
public class GecMcpToolsProvider implements ToolProvider {

    @Inject
    Vertx vertx;

    private static CopyOnWriteArrayList<McpClient> mcpClients = new CopyOnWriteArrayList<>();

    public void onStart(@Observes StartupEvent ev) {
        QuarkusHttpMcpTransport t = new QuarkusHttpMcpTransport.Builder()
                .sseUrl("http://localhost:8811/oncite-mcp/mcp/sse")
                .mcpClientName("MyMCPClient")
                .logRequests(true)
                .logResponses(true)
                .build();

//        QuarkusStreamableHttpMcpTransport t = new QuarkusStreamableHttpMcpTransport.Builder()
//                .url("https://oncite-dps-dev.apps.st.gcp.alm.oncite.io/oncite-mcp/mcp")
//                .httpClient(vertx.createHttpClient())
//                .logRequests(true)
//                .logResponses(true)
//                .build();
        McpClient mcpClient = new DefaultMcpClient.Builder()
                .key("MyMCPClient")
                .transport(t)
                .build();
        //TODO add more clients
        mcpClients.add(mcpClient);
    }

    public void onFinish(@Observes ShutdownEvent ev) {
        for (McpClient mcpClient : mcpClients) {
            try {
                mcpClient.close();
            } catch (Exception e) {
                throw new RuntimeException("Failed to close MCP Client", e);
            }
        }
    }

    @Override
    public ToolProviderResult provideTools(ToolProviderRequest request) {
        ToolProviderResult.Builder builder = ToolProviderResult.builder();

        for (McpClient mcpClient : mcpClients) {
            var defaultToolExecutor = new McpToolExecutor(mcpClient);
            try {
                mcpClient.listTools().stream()
                        .forEach(toolSpecification -> {
                            builder.add(toolSpecification, defaultToolExecutor);
                        });
            } catch (Exception e) {
                throw new RuntimeException("Failed to retrieve tools from MCP server", e);
            }
        }
        return builder.build();
    }

}

@RegisterAiService(maxSequentialToolInvocations = 50, 
        toolProviderSupplier = GecMcpToolsProviderSupplier.class)
@ApplicationScoped
public interface GecAiService {

My local started mcp server is getting called. But the result is the Toolname not the Result of the Tool Call. Any Hint???

[jmartisk]

Aaaaaargh, I mean McpToolProvider, not McpToolExecutor... Sorry - brain damage... replace every occurrence of Executor in that comment with Provider.

[jmartisk]

The point is that McpToolProvider takes care of the tool executors for you, you don't have to deal with them yourself.

[sberyozkin]

Sure, @KaiSuchomel, would you like to do a simple PR to have McpClientAuthProvider accepted by the builder ?
I guess the CDI resolution should be skipped if the builder provides it

[KaiSuchomel]

Sure, @KaiSuchomel, would you like to do a simple PR to have McpClientAuthProvider accepted by the builder ? I guess the CDI resolution should be skipped if the builder provides it

I will create one

[KaiSuchomel]

@sberyozkin I have created PR #1892 Will you have a look? Thx

[KaiSuchomel]

@jmartisk I finally get all working

@ApplicationScoped
public class GecMcpToolsProviderSupplier implements Supplier<ToolProvider> {

    private static CopyOnWriteArrayList<McpClient> mcpClients = new CopyOnWriteArrayList<>();

    @Inject
    Vertx vertx;

    @Inject
    MCPConfig mcpConfig;

    @Override
    public ToolProvider get() {
        for (Map.Entry<String, String> entry : mcpConfig.url().entrySet()) {
            String key = entry.getKey();
            String value = entry.getValue();
            QuarkusStreamableHttpMcpTransport t = new QuarkusStreamableHttpMcpTransport.Builder()
                    .url(value)
                    .httpClient(vertx.createHttpClient())
                    .logRequests(mcpConfig.logrequests())
                    .logResponses(mcpConfig.logresponses())
                    .mcpClientAuthProvider(new OidcMcpAuthProvider())
                    .build();
            McpClient mcpClient = new DefaultMcpClient.Builder()
                    .key(key)
                    .transport(t)
                    .cacheToolList(mcpConfig.cachetoollist())
                    .clientName(key)
                    .build();
            mcpClients.add(mcpClient);
        }
        return McpToolProvider.builder().mcpClients(mcpClients).build();
    }

    public void onShutdown(@Observes ShutdownEvent aShutdownEvent) {
        for (McpClient mcpClient : mcpClients) {
            try {
                mcpClient.close();
            } catch (Exception ex) {
                Log.error("GecMcpToolsProviderSupplier.onShutdown", ex);
            }
        }
    }

}

Thats all what to do. As soon as my PR is merged and released, we will use the ToolProvider from above. Thx for your help.

[KaiSuchomel]

@geoand When is the next release planned?

[geoand]

Whenever the last bugs have been addressed :).

Hopefully today or tomorrow

[geoand]

1.4.0.CR1 has been released