Creating a Wikipedia MCP Server in Java in a Few Prompts with Skills

///usr/bin/env jbang "$0" "$@" ; exit $?
//DEPS dev.langchain4j:langchain4j-core:1.11.0
//DEPS dev.langchain4j:langchain4j-community-mcp-server:1.11.0-beta19
//DEPS org.slf4j:slf4j-simple:2.0.17
//DEPS io.github.furstenheim:copy_down:1.1
//DEPS tools.jackson.core:jackson-databind:3.0.0-rc4
//JAVA 21

import dev.langchain4j.agent.tool.Tool;
import dev.langchain4j.community.mcp.server.McpServer;
import dev.langchain4j.community.mcp.server.transport.StdioMcpServerTransport;
import org.slf4j.Logger;
import org.slf4j.LoggerFactory;
import io.github.furstenheim.CopyDown;
import tools.jackson.databind.ObjectMapper;
import tools.jackson.databind.JsonNode;
import tools.jackson.databind.json.JsonMapper;

import java.net.URI;
import java.net.http.HttpClient;
import java.net.http.HttpRequest;
import java.net.http.HttpResponse;
import java.util.List;
import java.util.concurrent.CountDownLatch;
import java.net.URLEncoder;
import java.nio.charset.StandardCharsets;

public class WikipediaMcpServer {

    static {
        // Configure SLF4J Simple Logger to write to System.err
        // This is crucial for MCP servers over STDIO to avoid polluting stdout
        System.setProperty("org.slf4j.simpleLogger.logFile", "System.err");
    }

    private static final Logger log = LoggerFactory.getLogger(WikipediaMcpServer.class);

    public static void main(String[] args) throws Exception {
        log.info("Starting Wikipedia MCP Server...");

        WikipediaTools tools = new WikipediaTools();
        McpServer server = new McpServer(List.of(tools));
        StdioMcpServerTransport transport = new StdioMcpServerTransport(server);

        log.info("MCP Server started successfully on STDIO.");
        new CountDownLatch(1).await();
    }

    public static class WikipediaTools {
        private final HttpClient httpClient = HttpClient.newBuilder().followRedirects(HttpClient.Redirect.NORMAL).build();
        private final ObjectMapper objectMapper = JsonMapper.builder().build();
        private final CopyDown copyDown = new CopyDown();
        private final String USER_AGENT = "WikipediaMcpServer/1.0 (contact@example.com)";

        @Tool("Search Wikipedia for a given query and return a list of matching page titles and brief descriptions. Use this to find the exact page title before retrieving content.")
        public String searchWikipedia(String query) throws Exception {
            log.info("Searching Wikipedia for: {}", query);
            String encodedQuery = URLEncoder.encode(query, StandardCharsets.UTF_8);
            String url = "https://en.wikipedia.org/w/rest.php/v1/search/page?q=" + encodedQuery + "&limit=5";

            HttpRequest request = HttpRequest.newBuilder()
                    .uri(URI.create(url))
                    .header("User-Agent", USER_AGENT)
                    .GET()
                    .build();

            HttpResponse<String> response = httpClient.send(request, HttpResponse.BodyHandlers.ofString());

            if (response.statusCode() != 200) {
                return "Error searching Wikipedia: " + response.statusCode() + " - " + response.body();
            }

            JsonNode rootNode = objectMapper.readTree(response.body());
            JsonNode pagesNode = rootNode.get("pages");
            StringBuilder result = new StringBuilder("Search Results:\n\n");

            if (pagesNode != null && pagesNode.isArray()) {
                for (JsonNode page : pagesNode) {
                    String title = page.has("title") ? page.get("title").asText() : "";
                    String description = page.has("description") ? page.get("description").asText() : "No description";
                    result.append("- **").append(title).append("**: ").append(description).append("\n");
                }
            }

            if (result.length() == "Search Results:\n\n".length()) {
                return "No results found for query: " + query;
            }

            return result.toString();
        }

        @Tool("Retrieve the content of a specific Wikipedia page by its exact title, converted to Markdown format. Use the exact title returned by searchWikipedia.")
        public String getWikipediaPageContent(String title) throws Exception {
            log.info("Retrieving Wikipedia page: {}", title);
            String encodedTitle = URLEncoder.encode(title.replace(" ", "_"), StandardCharsets.UTF_8);
            String url = "https://en.wikipedia.org/api/rest_v1/page/html/" + encodedTitle;

            HttpRequest request = HttpRequest.newBuilder()
                    .uri(URI.create(url))
                    .header("User-Agent", USER_AGENT)
                    .GET()
                    .build();

            HttpResponse<String> response = httpClient.send(request, HttpResponse.BodyHandlers.ofString());

            if (response.statusCode() != 200) {
                return "Error retrieving Wikipedia page: " + response.statusCode() + " - " + response.body();
            }

            String htmlContent = response.body();
            log.info("Converting HTML to Markdown for page: {}", title);
            return copyDown.convert(htmlContent);
        }
    }
}

{
  "mcpServers": {
    "wikipedia-mcp": {
      "command": "jbang",
      "args": [
        "run",
        "--quiet",
        "/path/to/your/WikipediaMcpServer.java"
      ]
    }
  }
}