Client configuration for mcp server which needs Api key as authentication

[ekizy]

Hi,
I want to connect to a mcp server which uses api key as authentication and I need to use McpAsyncClient. I researched a lot but could not find a proper solution since options are limited.

Can you help me with that how I can do it ?

I am using this one

        <artifactId>spring-ai-starter-mcp-client-webflux</artifactId>

[Kehrlann]

Hi! What you need is the section of the README about customizing HTTP requests.

@Configuration
class McpConfiguration {

    @Bean
    WebClient.Builder mcpWebClientBuilder() {
        return WebClient.builder().filter((request, next) -> {
            var newRequest = ClientRequest.from(request)
                    .header("x-custom-header", "custom-value")
                    .header("x-life-the-universe-everything", "42")
                    .build();
            return next.exchange(newRequest);
        });
    }

}

[ekizy]

Thanks a lot for the answer would it be a way to use this filter only for one specific server, if we need to connect 2 mcp servers and one of them needs the api key header but one not

and in a weird in requests after applying these filters, I see the domains/mcp twice that confused me little bit too

[Kehrlann]

Two solutions:

Conditional filtering

Decided whether to add the API key in the filter itself

@Bean
WebClient.Builder mcpWebClientBuilder() {
    return WebClient.builder().filter((request, next) -> {
        if (request.url().getHost().equals("api.example.com")) {
            var newRequest = ClientRequest.from(request)
                .header("x-custom-header", "custom-value")
                .header("x-life-the-universe-everything", "42")
                .build();
            return next.exchange(newRequest);
        } else {
            return next.exchange(request);
        }
    });
}

Manual creation of MCP transports

You'd have to do the equivalent of what Spring AI's StreamableHttpWebFluxTransportAutoConfiguration does here; so probably something like:

@Bean
public List<NamedClientMcpTransport> streamableHttpWebFluxClientTransports(
        ObjectProvider<ObjectMapper> objectMapperProvider) {
    List<NamedClientMcpTransport> streamableHttpTransports = new ArrayList<>();

    var builder = mcpClientBuilder("https://simple.example.com", false);
    var builderWithApiKey = mcpClientBuilder("https://api.example.com",true);
    var objectMapper = objectMapperProvider.getIfAvailable(ObjectMapper::new);

    var transport = WebClientStreamableHttpTransport.builder(builder)
            .jsonMapper(new JacksonMcpJsonMapper(objectMapper))
            .build();
    streamableHttpTransports.add(new NamedClientMcpTransport("simple", transport));

    var apiKeyTransport = WebClientStreamableHttpTransport.builder(builderWithApiKey)
            .jsonMapper(new JacksonMcpJsonMapper(objectMapper))
            .build();
    streamableHttpTransports.add(new NamedClientMcpTransport("apikey", apiKeyTransport));
    
    return streamableHttpTransports;
}

In this case, you probably want to avoid spring.ai.mcp.client.streamable-http.connections.* properties ; as you're building the transports yourself.