feat: Improve Tool schema handling

- Make McpSchema final and add private constructor
- Add JsonSchema record for structured schema representation
- Change Tool.inputSchema type from Map<String, Object> to JsonSchema.
- Use the String JSON Schema constructor when creating the Tool programaticaly.
- Enhance StdioClientTransport error logging with more context
- Add ToolHelper utility class for:
  - Converting Spring AI FunctionCallbacks to MCP tools
  - Generating JSON schemas for tool input validation
  - Facilitating integration between Spring AI functions and MCP tools
- Update tests and samples to use the new Tool schema format

Resolves #52

spring-ai-mcp-sample/pom.xml

@@ -20,7 +20,7 @@
     <dependencies>
         <dependency>
             <groupId>org.springframework.experimental</groupId>
-            <artifactId>mcp</artifactId>
+            <artifactId>spring-ai-mcp</artifactId>
             <version>${project.version}</version>
         </dependency>
 

spring-ai-mcp-sample/src/main/java/org/springframework/ai/mcp/sample/client/SampleClient.java

@@ -58,6 +58,13 @@ public class SampleClient {
 			.callTool(new CallToolRequest("calculator", Map.of("operation", "multiply", "a", 2.0, "b", 3.0)));
 		System.out.println("Calculator Response = " + calcResponse);
 
+		CallToolResult paymentStatus = client.callTool(
+				new CallToolRequest("paymentTransactionStatus", Map.of("transactionId", "006", "accountName", "John")));
+		System.out.println("Payment Status Response = " + paymentStatus);
+
+		CallToolResult parks = client.callTool(new CallToolRequest("getBooks", Map.of("title", "Spring Framework")));
+		System.out.println("Books Response = " + parks);
+
 		// List and demonstrate resources
 		var resourcesList = client.listResources();
 		System.out.println("\nAvailable Resources = " + resourcesList);

spring-ai-mcp-sample/src/main/java/org/springframework/ai/mcp/sample/server/McpServerConfig.java

@@ -2,6 +2,7 @@ package org.springframework.ai.mcp.sample.server;
 
 import java.util.List;
 import java.util.Map;
+import java.util.function.Function;
 
 import com.fasterxml.jackson.databind.ObjectMapper;
 import org.slf4j.Logger;
@@ -21,10 +22,14 @@ import org.springframework.ai.mcp.spec.McpSchema.LoggingMessageNotification;
 import org.springframework.ai.mcp.spec.McpSchema.PromptMessage;
 import org.springframework.ai.mcp.spec.McpSchema.Role;
 import org.springframework.ai.mcp.spec.McpSchema.TextContent;
+import org.springframework.ai.mcp.spec.McpSchema.Tool;
 import org.springframework.ai.mcp.spec.ServerMcpTransport;
+import org.springframework.ai.mcp.spring.ToolHelper;
+import org.springframework.ai.model.function.FunctionCallback;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.Configuration;
+import org.springframework.web.client.RestClient;
 import org.springframework.web.reactive.function.server.RouterFunction;
 
 @Configuration
@@ -55,7 +60,7 @@ public class McpServerConfig {
 	}
 
 	@Bean
-	public McpAsyncServer mcpServer(ServerMcpTransport transport) { // @formatter:off
+	public McpAsyncServer mcpServer(ServerMcpTransport transport, OpenLibrary openLibrary) { // @formatter:off
 
 		// Configure server capabilities with resource support
 		var capabilities = McpSchema.ServerCapabilities.builder()
@@ -71,13 +76,48 @@ public class McpServerConfig {
 			.capabilities(capabilities)
 			.resources(systemInfoResourceRegistration())
 			.prompts(greetingPromptRegistration())
-			.tools(calculatorToolRegistration())
+			.tools(calculatorToolRegistration(),
+				ToolHelper.toToolRegistration(
+					FunctionCallback.builder()
+						.description("Get transaction payment status")
+						.method("paymentTransactionStatus",String.class, String.class)
+						.targetClass(McpServerConfig.class)
+					.build()),
+				ToolHelper.toToolRegistration(
+					FunctionCallback.builder()
+						.description("To upper case")
+						.function("toUpperCase", new Function<String, String>() {
+							@Override
+							public String apply(String s) {
+								return s.toUpperCase();
+							}
+						})
+						.inputType(String.class)						
+					.build()))
+			.tools(openLibraryToolRegistrations(openLibrary))
 			.async();
 		
 		server.addTool(weatherToolRegistration(server));
 		return server; // @formatter:on
 	} // @formatter:on
 
+	public static List<ToolRegistration> openLibraryToolRegistrations(OpenLibrary openLibrary) {
+
+		var books = FunctionCallback.builder()
+			.description("Get list of Books by title")
+			.method("getBooks", String.class)
+			.targetObject(openLibrary)
+			.build();
+
+		var bookTitlesByAuthor = FunctionCallback.builder()
+			.description("Get book titles by author")
+			.method("getBookTitlesByAuthor", String.class)
+			.targetObject(openLibrary)
+			.build();
+
+		return ToolHelper.toToolRegistration(books, bookTitlesByAuthor);
+	}
+
 	private static ResourceRegistration systemInfoResourceRegistration() {
 
 		// Create a resource registration for system information
@@ -131,8 +171,14 @@ public class McpServerConfig {
 	}
 
 	private static ToolRegistration weatherToolRegistration(McpAsyncServer server) {
-		return new ToolRegistration(
-				new McpSchema.Tool("weather", "Weather forecast tool by location", Map.of("city", "String")),
+		String emptyJsonSchema = """
+				{
+					"$schema": "http://json-schema.org/draft-07/schema#",
+					"type": "object",
+					"properties": {"city" : "string"}
+				}
+				""";
+		return new ToolRegistration(new McpSchema.Tool("weather", "Weather forecast tool by location", emptyJsonSchema),
 				(arguments) -> {
 					String city = (String) arguments.get("city");
 
@@ -210,4 +256,17 @@ public class McpServerConfig {
 				});
 	}
 
+	public static String paymentTransactionStatus(String transactionId, String accountName) {
+		return "The status for " + transactionId + ", by " + accountName + " is PENDING";
+	}
+
+	public Function<String, String> toUpperCase() {
+		return String::toUpperCase;
+	}
+
+	@Bean
+	public OpenLibrary openLibrary() {
+		return new OpenLibrary(RestClient.builder());
+	}
+
 }

spring-ai-mcp-sample/src/main/java/org/springframework/ai/mcp/sample/server/OpenLibrary.java

@@ -0,0 +1,74 @@
+/*
+* Copyright 2024 - 2024 the original author or authors.
+*
+* Licensed under the Apache License, Version 2.0 (the "License");
+* you may not use this file except in compliance with the License.
+* You may obtain a copy of the License at
+*
+* https://www.apache.org/licenses/LICENSE-2.0
+*
+* Unless required by applicable law or agreed to in writing, software
+* distributed under the License is distributed on an "AS IS" BASIS,
+* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+* See the License for the specific language governing permissions and
+* limitations under the License.
+*/
+package org.springframework.ai.mcp.sample.server;
+
+import java.util.List;
+import java.util.Map;
+
+import org.springframework.web.client.RestClient;
+
+/**
+ * @author Christian Tzolov
+ */
+
+public class OpenLibrary {
+
+	private RestClient restClient;
+
+	public OpenLibrary(RestClient.Builder restClientBuilder) {
+		this.restClient = restClientBuilder.baseUrl("https://openlibrary.org").build();
+	}
+
+	public record Books(Integer numFound, Integer start, Boolean numFoundExact, List<Map<String, Object>> docs) {
+	}
+
+	public record Book(List<String> isbn, String title, List<String> authorName) {
+	}
+
+	public List<Book> getBooks(String title) {
+		Books books = restClient.get()
+			.uri(uriBuilder -> uriBuilder.path("/search.json").queryParam("q", title).build())
+			.retrieve()
+			.body(Books.class);
+		if (books == null) {
+			return List.of();
+		}
+		return books.docs.stream()
+			.map(doc -> new Book((List<String>) doc.get("isbn"), (String) doc.get("title"),
+					(List<String>) doc.get("author_name")))
+			.toList();
+	}
+
+	public List<String> getBookTitlesByAuthor(String authorName) {
+		var books = restClient.get()
+			.uri(uriBuilder -> uriBuilder.path("/search/authors.json").queryParam("q", authorName).build())
+			.retrieve()
+			.body(Books.class);
+		if (books == null) {
+			return List.of();
+		}
+		return books.docs.stream().map(doc -> (String) doc.get("top_work")).toList();
+	}
+
+	public static void main(String[] args) {
+		OpenLibrary openLibrary = new OpenLibrary(RestClient.builder());
+		List<Book> books = openLibrary.getBooks("Spring Framework");
+		System.out.println(books);
+		List<String> booksByAuthor = openLibrary.getBookTitlesByAuthor("Craig Walls");
+		System.out.println(booksByAuthor);
+	}
+
+}

spring-ai-mcp-sample/src/main/resources/application.properties

@@ -1,16 +1,8 @@
-# Server port
-# server.port=8080
-
-# Logging
-# logging.level.org.springframework.ai.mcp=DEBUG
-# logging.level.org.springframework.web=INFO
-
-spring.main.banner-mode=off
-# logging.level.root=OFF
 # spring.main.web-application-type=none
-# logging.pattern.console=
-logging.level.org.springframework.ai.mcp.*=OFF
-logging.level.org.springframework.ai.mcp.spec.*=OFF
-logging.level.org.springframework.**=OFF
+
+# NOTE: You must disable the banner and the console logging 
+# to allow the STDIO transport to work !!!
+spring.main.banner-mode=off
+logging.pattern.console=
 
 transport.mode=sse