feat: add progress token support and extend Request interface (#352)

- Add PaginatedRequest and ReadResourceRequest to Request sealed interface
- Add default meta() and progressToken() methods to Request interface
- Add _meta parameter support to request classes:
  - ReadResourceRequest, GetPromptRequest, CallToolRequest
  - CreateMessageRequest, ElicitRequest, CompleteRequest, PaginatedRequest
- Add builder methods for progress token configuration
- Add message field to ProgressNotification
- Maintain backward compatibility with existing constructors
- Add _meta field to the InitialRequest record

Signed-off-by: Christian Tzolov <christian.tzolov@broadcom.com>

mcp/src/main/java/io/modelcontextprotocol/spec/McpSchema.java

@@ -142,7 +142,16 @@ public final class McpSchema {
 	}
 
 	public sealed interface Request permits InitializeRequest, CallToolRequest, CreateMessageRequest, ElicitRequest,
-			CompleteRequest, GetPromptRequest {
+			CompleteRequest, GetPromptRequest, PaginatedRequest, ReadResourceRequest {
+
+		Map<String, Object> meta();
+
+		default String progressToken() {
+			if (meta() != null && meta().containsKey("progressToken")) {
+				return meta().get("progressToken").toString();
+			}
+			return null;
+		}
 
 	}
 
@@ -237,7 +246,12 @@ public final class McpSchema {
 	public record InitializeRequest( // @formatter:off
                 @JsonProperty("protocolVersion") String protocolVersion,
                 @JsonProperty("capabilities") ClientCapabilities capabilities,
-		@JsonProperty("clientInfo") Implementation clientInfo) implements Request {
+                @JsonProperty("clientInfo") Implementation clientInfo,
+				@JsonProperty("_meta") Map<String, Object> meta) implements Request {
+			
+			public InitializeRequest(String protocolVersion, ClientCapabilities capabilities, Implementation clientInfo) {
+				this(protocolVersion, capabilities, clientInfo, null);
+			}
         } // @formatter:on
 
 	@JsonInclude(JsonInclude.Include.NON_ABSENT)
@@ -630,7 +644,12 @@ public final class McpSchema {
 	@JsonInclude(JsonInclude.Include.NON_ABSENT)
 	@JsonIgnoreProperties(ignoreUnknown = true)
 	public record ReadResourceRequest( // @formatter:off
-		@JsonProperty("uri") String uri){
+                @JsonProperty("uri") String uri,
+                @JsonProperty("_meta") Map<String, Object> meta) implements Request {
+
+                public ReadResourceRequest(String uri) {
+                        this(uri, null);
+                }
         } // @formatter:on
 
 	@JsonInclude(JsonInclude.Include.NON_ABSENT)
@@ -786,7 +805,12 @@ public final class McpSchema {
 	@JsonIgnoreProperties(ignoreUnknown = true)
 	public record GetPromptRequest(// @formatter:off
                 @JsonProperty("name") String name,
-		@JsonProperty("arguments") Map<String, Object> arguments) implements Request {
+                @JsonProperty("arguments") Map<String, Object> arguments,
+                @JsonProperty("_meta") Map<String, Object> meta) implements Request {
+
+                public GetPromptRequest(String name, Map<String, Object> arguments) {
+                        this(name, arguments, null);
+                }
         }// @formatter:off
 
         /**
@@ -894,10 +918,14 @@ public final class McpSchema {
 	@JsonIgnoreProperties(ignoreUnknown = true)
 	public record CallToolRequest(// @formatter:off
                 @JsonProperty("name") String name,
-		@JsonProperty("arguments") Map<String, Object> arguments) implements Request {
+                @JsonProperty("arguments") Map<String, Object> arguments,
+                @JsonProperty("_meta") Map<String, Object> meta) implements Request {
 
                 public CallToolRequest(String name, String jsonArguments) {
-			this(name, parseJsonArguments(jsonArguments));
+                        this(name, parseJsonArguments(jsonArguments), null);
+                }
+                public CallToolRequest(String name, Map<String, Object> arguments) {
+                        this(name, arguments, null);
                 }
 
                 private static Map<String, Object> parseJsonArguments(String jsonArguments) {
@@ -908,6 +936,49 @@ public final class McpSchema {
                                 throw new IllegalArgumentException("Invalid arguments: " + jsonArguments, e);
                         }
                 }
+
+                public static Builder builder() {
+                        return new Builder();
+                }
+
+                public static class Builder {
+                        private String name;
+                        private Map<String, Object> arguments;
+                        private Map<String, Object> meta;
+
+                        public Builder name(String name) {
+                                this.name = name;
+                                return this;
+                        }
+
+                        public Builder arguments(Map<String, Object> arguments) {
+                                this.arguments = arguments;
+                                return this;
+                        }
+
+                        public Builder arguments(String jsonArguments) {
+                                this.arguments = parseJsonArguments(jsonArguments);
+                                return this;
+                        }
+
+                        public Builder meta(Map<String, Object> meta) {
+                                this.meta = meta;
+                                return this;
+                        }
+
+                        public Builder progressToken(String progressToken) {
+                                if (this.meta == null) {
+                                        this.meta = new HashMap<>();
+                                }
+                                this.meta.put("progressToken", progressToken);
+                                return this;
+                        }
+
+                        public CallToolRequest build() {
+                                Assert.hasText(name, "name must not be empty");
+                                return new CallToolRequest(name, arguments, meta);
+                        }
+                }
         }// @formatter:off
 
         /**
@@ -1103,7 +1174,18 @@ public final class McpSchema {
                 @JsonProperty("temperature") Double temperature,
                 @JsonProperty("maxTokens") int maxTokens,
                 @JsonProperty("stopSequences") List<String> stopSequences,
-		@JsonProperty("metadata") Map<String, Object> metadata) implements Request {
+                @JsonProperty("metadata") Map<String, Object> metadata,
+				@JsonProperty("_meta") Map<String, Object> meta) implements Request {
+
+				
+				// backwards compatibility constructor
+				public CreateMessageRequest(List<SamplingMessage> messages, ModelPreferences modelPreferences,
+											String systemPrompt, ContextInclusionStrategy includeContext,
+											Double temperature, int maxTokens, List<String> stopSequences,
+											Map<String, Object> metadata) {
+						this(messages, modelPreferences, systemPrompt, includeContext, temperature, maxTokens,
+								stopSequences, metadata, null);
+				}
 
                 public enum ContextInclusionStrategy {
                         @JsonProperty("none") NONE,
@@ -1124,6 +1206,7 @@ public final class McpSchema {
                         private int maxTokens;
                         private List<String> stopSequences;
                         private Map<String, Object> metadata;
+						private Map<String, Object> meta;
 
                         public Builder messages(List<SamplingMessage> messages) {
                                 this.messages = messages;
@@ -1165,9 +1248,22 @@ public final class McpSchema {
                                 return this;
                         }
 
+						public Builder meta(Map<String, Object> meta) {
+								this.meta = meta;
+								return this;
+						}
+
+						public Builder progressToken(String progressToken) {
+								if (this.meta == null) {
+										this.meta = new HashMap<>();
+								}
+								this.meta.put("progressToken", progressToken);
+								return this;
+						}
+
                         public CreateMessageRequest build() {
                                 return new CreateMessageRequest(messages, modelPreferences, systemPrompt,
-					includeContext, temperature, maxTokens, stopSequences, metadata);
+                                        includeContext, temperature, maxTokens, stopSequences, metadata, meta);
                         }
                 }
         }// @formatter:on
@@ -1253,7 +1349,13 @@ public final class McpSchema {
 	@JsonIgnoreProperties(ignoreUnknown = true)
 	public record ElicitRequest(// @formatter:off
                 @JsonProperty("message") String message,
-		@JsonProperty("requestedSchema") Map<String, Object> requestedSchema) implements Request {
+                @JsonProperty("requestedSchema") Map<String, Object> requestedSchema,
+				@JsonProperty("_meta") Map<String, Object> meta) implements Request {
+
+				// backwards compatibility constructor
+				public ElicitRequest(String message, Map<String, Object> requestedSchema) {
+						this(message, requestedSchema, null);
+				}
 
                 public static Builder builder() {
                         return new Builder();
@@ -1262,6 +1364,7 @@ public final class McpSchema {
                 public static class Builder {
                         private String message;
                         private Map<String, Object> requestedSchema;
+						private Map<String, Object> meta;
 
                         public Builder message(String message) {
                                 this.message = message;
@@ -1273,8 +1376,21 @@ public final class McpSchema {
                                 return this;
                         }
 
+						public Builder meta(Map<String, Object> meta) {
+								this.meta = meta;
+								return this;
+						}
+
+						public Builder progressToken(String progressToken) {
+								if (this.meta == null) {
+										this.meta = new HashMap<>();
+								}
+								this.meta.put("progressToken", progressToken);
+								return this;
+						}
+
                         public ElicitRequest build() {
-				return new ElicitRequest(message, requestedSchema);
+                                return new ElicitRequest(message, requestedSchema, meta);
                         }
                 }
         }// @formatter:on
@@ -1320,7 +1436,20 @@ public final class McpSchema {
 	// ---------------------------
 	@JsonInclude(JsonInclude.Include.NON_ABSENT)
 	@JsonIgnoreProperties(ignoreUnknown = true)
-	public record PaginatedRequest(@JsonProperty("cursor") String cursor) {
+	public record PaginatedRequest(// @formatter:off
+                @JsonProperty("cursor") String cursor,
+                @JsonProperty("_meta") Map<String, Object> meta) implements Request { // @formatter:on
+
+		public PaginatedRequest(String cursor) {
+			this(cursor, null);
+		}
+
+		/**
+		 * Creates a new paginated request with an empty cursor.
+		 */
+		public PaginatedRequest() {
+			this(null);
+		}
 	}
 
 	@JsonInclude(JsonInclude.Include.NON_ABSENT)
@@ -1331,11 +1460,24 @@ public final class McpSchema {
 	// ---------------------------
 	// Progress and Logging
 	// ---------------------------
+	/**
+	 * The Model Context Protocol (MCP) supports optional progress tracking for
+	 * long-running operations through notification messages. Either side can send
+	 * progress notifications to provide updates about operation status.
+	 *
+	 * @param progressToken A unique token to identify the progress notification. MUST be
+	 * unique across all active requests.
+	 * @param progress A value indicating the current progress.
+	 * @param total An optional total amount of work to be done, if known.
+	 * @param message An optional message providing additional context about the progress.
+	 */
+	@JsonInclude(JsonInclude.Include.NON_ABSENT)
 	@JsonIgnoreProperties(ignoreUnknown = true)
 	public record ProgressNotification(// @formatter:off
                 @JsonProperty("progressToken") String progressToken,
-		@JsonProperty("progress") double progress,
+                @JsonProperty("progress") Double progress,
-		@JsonProperty("total") Double total) {
+                @JsonProperty("total") Double total,
+				@JsonProperty("message") String message) {
         }// @formatter:on
 
 	/**
@@ -1469,7 +1611,12 @@ public final class McpSchema {
 	@JsonIgnoreProperties(ignoreUnknown = true)
 	public record CompleteRequest(// @formatter:off
                 @JsonProperty("ref") McpSchema.CompleteReference ref,
-		@JsonProperty("argument") CompleteArgument argument) implements Request {
+                @JsonProperty("argument") CompleteArgument argument,
+                @JsonProperty("_meta") Map<String, Object> meta) implements Request {
+
+                public CompleteRequest(McpSchema.CompleteReference ref, CompleteArgument argument) {
+                        this(ref, argument, null);
+                }
 
                 public record CompleteArgument(
                         @JsonProperty("name") String name,

mcp/src/test/java/io/modelcontextprotocol/spec/McpSchemaTests.java

@@ -3,22 +3,23 @@
 */
 package io.modelcontextprotocol.spec;
 
+import static net.javacrumbs.jsonunit.assertj.JsonAssertions.assertThatJson;
+import static net.javacrumbs.jsonunit.assertj.JsonAssertions.json;
+import static org.assertj.core.api.Assertions.assertThat;
+import static org.assertj.core.api.Assertions.assertThatThrownBy;
+
 import java.util.Arrays;
 import java.util.Collections;
 import java.util.HashMap;
 import java.util.List;
 import java.util.Map;
 
-import static org.assertj.core.api.Assertions.assertThat;
-import static org.assertj.core.api.Assertions.assertThatThrownBy;
 import org.junit.jupiter.api.Test;
 
 import com.fasterxml.jackson.databind.ObjectMapper;
 import com.fasterxml.jackson.databind.exc.InvalidTypeIdException;
 
 import io.modelcontextprotocol.spec.McpSchema.TextResourceContents;
-import static net.javacrumbs.jsonunit.assertj.JsonAssertions.assertThatJson;
-import static net.javacrumbs.jsonunit.assertj.JsonAssertions.json;
 import net.javacrumbs.jsonunit.core.Option;
 
 /**
@@ -106,6 +107,43 @@ public class McpSchemaTests {
 		assertThat(audioContent.mimeType()).isEqualTo("audio/wav");
 	}
 
+	@Test
+	void testCreateMessageRequestWithMeta() throws Exception {
+		McpSchema.TextContent content = new McpSchema.TextContent("User message");
+		McpSchema.SamplingMessage message = new McpSchema.SamplingMessage(McpSchema.Role.USER, content);
+		McpSchema.ModelHint hint = new McpSchema.ModelHint("gpt-4");
+		McpSchema.ModelPreferences preferences = new McpSchema.ModelPreferences(Collections.singletonList(hint), 0.3,
+				0.7, 0.9);
+
+		Map<String, Object> metadata = new HashMap<>();
+		metadata.put("session", "test-session");
+
+		Map<String, Object> meta = new HashMap<>();
+		meta.put("progressToken", "create-message-token-456");
+
+		McpSchema.CreateMessageRequest request = McpSchema.CreateMessageRequest.builder()
+			.messages(Collections.singletonList(message))
+			.modelPreferences(preferences)
+			.systemPrompt("You are a helpful assistant")
+			.includeContext(McpSchema.CreateMessageRequest.ContextInclusionStrategy.THIS_SERVER)
+			.temperature(0.7)
+			.maxTokens(1000)
+			.stopSequences(Arrays.asList("STOP", "END"))
+			.metadata(metadata)
+			.meta(meta)
+			.build();
+
+		String value = mapper.writeValueAsString(request);
+		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
+			.when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
+			.isObject()
+			.containsEntry("_meta", Map.of("progressToken", "create-message-token-456"));
+
+		// Test Request interface methods
+		assertThat(request.meta()).isEqualTo(meta);
+		assertThat(request.progressToken()).isEqualTo("create-message-token-456");
+	}
+
 	@Test
 	void testEmbeddedResource() throws Exception {
 		McpSchema.TextResourceContents resourceContents = new McpSchema.TextResourceContents("resource://test",
@@ -444,6 +482,36 @@ public class McpSchemaTests {
 					{"uri":"resource://test"}"""));
 	}
 
+	@Test
+	void testReadResourceRequestWithMeta() throws Exception {
+		Map<String, Object> meta = new HashMap<>();
+		meta.put("progressToken", "read-resource-token-123");
+
+		McpSchema.ReadResourceRequest request = new McpSchema.ReadResourceRequest("resource://test", meta);
+
+		String value = mapper.writeValueAsString(request);
+		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
+			.when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
+			.isObject()
+			.isEqualTo(json("""
+					{"uri":"resource://test","_meta":{"progressToken":"read-resource-token-123"}}"""));
+
+		// Test Request interface methods
+		assertThat(request.meta()).isEqualTo(meta);
+		assertThat(request.progressToken()).isEqualTo("read-resource-token-123");
+	}
+
+	@Test
+	void testReadResourceRequestDeserialization() throws Exception {
+		McpSchema.ReadResourceRequest request = mapper.readValue("""
+				{"uri":"resource://test","_meta":{"progressToken":"test-token"}}""",
+				McpSchema.ReadResourceRequest.class);
+
+		assertThat(request.uri()).isEqualTo("resource://test");
+		assertThat(request.meta()).containsEntry("progressToken", "test-token");
+		assertThat(request.progressToken()).isEqualTo("test-token");
+	}
+
 	@Test
 	void testReadResourceResult() throws Exception {
 		McpSchema.TextResourceContents contents1 = new McpSchema.TextResourceContents("resource://test1", "text/plain",
@@ -529,6 +597,30 @@ public class McpSchemaTests {
 			.isEqualTo(request);
 	}
 
+	@Test
+	void testGetPromptRequestWithMeta() throws Exception {
+		Map<String, Object> arguments = new HashMap<>();
+		arguments.put("arg1", "value1");
+		arguments.put("arg2", 42);
+
+		Map<String, Object> meta = new HashMap<>();
+		meta.put("progressToken", "token123");
+
+		McpSchema.GetPromptRequest request = new McpSchema.GetPromptRequest("test-prompt", arguments, meta);
+
+		String value = mapper.writeValueAsString(request);
+		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
+			.when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
+			.isObject()
+			.isEqualTo(
+					json("""
+							{"name":"test-prompt","arguments":{"arg1":"value1","arg2":42},"_meta":{"progressToken":"token123"}}"""));
+
+		// Test that it implements Request interface methods
+		assertThat(request.meta()).isEqualTo(meta);
+		assertThat(request.progressToken()).isEqualTo("token123");
+	}
+
 	@Test
 	void testGetPromptResult() throws Exception {
 		McpSchema.TextContent content1 = new McpSchema.TextContent("System message");
@@ -775,6 +867,65 @@ public class McpSchemaTests {
 					{"name":"test-tool","arguments":{"name":"test","value":42}}"""));
 	}
 
+	@Test
+	void testCallToolRequestWithMeta() throws Exception {
+
+		McpSchema.CallToolRequest request = McpSchema.CallToolRequest.builder()
+			.name("test-tool")
+			.arguments(Map.of("name", "test", "value", 42))
+			.progressToken("tool-progress-123")
+			.build();
+		String value = mapper.writeValueAsString(request);
+
+		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
+			.when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
+			.isObject()
+			.isEqualTo(
+					json("""
+							{"name":"test-tool","arguments":{"name":"test","value":42},"_meta":{"progressToken":"tool-progress-123"}}"""));
+
+		// Test that it implements Request interface methods
+		assertThat(request.meta()).isEqualTo(Map.of("progressToken", "tool-progress-123"));
+		assertThat(request.progressToken()).isEqualTo("tool-progress-123");
+	}
+
+	@Test
+	void testCallToolRequestBuilderWithJsonArguments() throws Exception {
+		Map<String, Object> meta = new HashMap<>();
+		meta.put("progressToken", "json-builder-789");
+
+		McpSchema.CallToolRequest request = McpSchema.CallToolRequest.builder().name("test-tool").arguments("""
+				{
+					"name": "test",
+					"value": 42
+				}
+				""").meta(meta).build();
+
+		String value = mapper.writeValueAsString(request);
+
+		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
+			.when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
+			.isObject()
+			.isEqualTo(
+					json("""
+							{"name":"test-tool","arguments":{"name":"test","value":42},"_meta":{"progressToken":"json-builder-789"}}"""));
+
+		// Test that it implements Request interface methods
+		assertThat(request.meta()).isEqualTo(meta);
+		assertThat(request.progressToken()).isEqualTo("json-builder-789");
+	}
+
+	@Test
+	void testCallToolRequestBuilderNameRequired() {
+		Map<String, Object> arguments = new HashMap<>();
+		arguments.put("name", "test");
+
+		McpSchema.CallToolRequest.Builder builder = McpSchema.CallToolRequest.builder().arguments(arguments);
+
+		assertThatThrownBy(builder::build).isInstanceOf(IllegalArgumentException.class)
+			.hasMessageContaining("name must not be empty");
+	}
+
 	@Test
 	void testCallToolResult() throws Exception {
 		McpSchema.TextContent content = new McpSchema.TextContent("Tool execution result");
@@ -991,6 +1142,141 @@ public class McpSchemaTests {
 					{"action":"accept","content":{"foo":"bar"}}"""));
 	}
 
+	@Test
+	void testElicitRequestWithMeta() throws Exception {
+		Map<String, Object> requestedSchema = Map.of("type", "object", "required", List.of("name"), "properties",
+				Map.of("name", Map.of("type", "string")));
+
+		Map<String, Object> meta = new HashMap<>();
+		meta.put("progressToken", "elicit-token-789");
+
+		McpSchema.ElicitRequest request = McpSchema.ElicitRequest.builder()
+			.message("Please provide your name")
+			.requestedSchema(requestedSchema)
+			.meta(meta)
+			.build();
+
+		String value = mapper.writeValueAsString(request);
+		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
+			.when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
+			.isObject()
+			.containsEntry("_meta", Map.of("progressToken", "elicit-token-789"));
+
+		// Test Request interface methods
+		assertThat(request.meta()).isEqualTo(meta);
+		assertThat(request.progressToken()).isEqualTo("elicit-token-789");
+	}
+
+	// Pagination Tests
+
+	@Test
+	void testPaginatedRequestNoArgs() throws Exception {
+		McpSchema.PaginatedRequest request = new McpSchema.PaginatedRequest();
+
+		String value = mapper.writeValueAsString(request);
+		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
+			.when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
+			.isObject()
+			.isEqualTo(json("""
+					{}"""));
+
+		// Test that it implements Request interface methods
+		assertThat(request.meta()).isNull();
+		assertThat(request.progressToken()).isNull();
+	}
+
+	@Test
+	void testPaginatedRequestWithCursor() throws Exception {
+		McpSchema.PaginatedRequest request = new McpSchema.PaginatedRequest("cursor123");
+
+		String value = mapper.writeValueAsString(request);
+		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
+			.when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
+			.isObject()
+			.isEqualTo(json("""
+					{"cursor":"cursor123"}"""));
+
+		// Test that it implements Request interface methods
+		assertThat(request.meta()).isNull();
+		assertThat(request.progressToken()).isNull();
+	}
+
+	@Test
+	void testPaginatedRequestWithMeta() throws Exception {
+		Map<String, Object> meta = new HashMap<>();
+		meta.put("progressToken", "pagination-progress-456");
+
+		McpSchema.PaginatedRequest request = new McpSchema.PaginatedRequest("cursor123", meta);
+
+		String value = mapper.writeValueAsString(request);
+		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
+			.when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
+			.isObject()
+			.isEqualTo(json("""
+					{"cursor":"cursor123","_meta":{"progressToken":"pagination-progress-456"}}"""));
+
+		// Test that it implements Request interface methods
+		assertThat(request.meta()).isEqualTo(meta);
+		assertThat(request.progressToken()).isEqualTo("pagination-progress-456");
+	}
+
+	@Test
+	void testPaginatedRequestDeserialization() throws Exception {
+		McpSchema.PaginatedRequest request = mapper.readValue("""
+				{"cursor":"test-cursor","_meta":{"progressToken":"test-token"}}""", McpSchema.PaginatedRequest.class);
+
+		assertThat(request.cursor()).isEqualTo("test-cursor");
+		assertThat(request.meta()).containsEntry("progressToken", "test-token");
+		assertThat(request.progressToken()).isEqualTo("test-token");
+	}
+
+	// Complete Request Tests
+
+	@Test
+	void testCompleteRequest() throws Exception {
+		McpSchema.PromptReference promptRef = new McpSchema.PromptReference("test-prompt");
+		McpSchema.CompleteRequest.CompleteArgument argument = new McpSchema.CompleteRequest.CompleteArgument("arg1",
+				"partial-value");
+
+		McpSchema.CompleteRequest request = new McpSchema.CompleteRequest(promptRef, argument);
+
+		String value = mapper.writeValueAsString(request);
+		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
+			.when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
+			.isObject()
+			.isEqualTo(
+					json("""
+							{"ref":{"type":"ref/prompt","name":"test-prompt"},"argument":{"name":"arg1","value":"partial-value"}}"""));
+
+		// Test that it implements Request interface methods
+		assertThat(request.meta()).isNull();
+		assertThat(request.progressToken()).isNull();
+	}
+
+	@Test
+	void testCompleteRequestWithMeta() throws Exception {
+		McpSchema.ResourceReference resourceRef = new McpSchema.ResourceReference("file:///test.txt");
+		McpSchema.CompleteRequest.CompleteArgument argument = new McpSchema.CompleteRequest.CompleteArgument("path",
+				"/partial/path");
+
+		Map<String, Object> meta = new HashMap<>();
+		meta.put("progressToken", "complete-progress-789");
+
+		McpSchema.CompleteRequest request = new McpSchema.CompleteRequest(resourceRef, argument, meta);
+
+		String value = mapper.writeValueAsString(request);
+		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
+			.when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
+			.isObject()
+			.isEqualTo(
+					json("""
+							{"ref":{"type":"ref/resource","uri":"file:///test.txt"},"argument":{"name":"path","value":"/partial/path"},"_meta":{"progressToken":"complete-progress-789"}}"""));
+
+		// Test that it implements Request interface methods
+		assertThat(request.meta()).isEqualTo(meta);
+		assertThat(request.progressToken()).isEqualTo("complete-progress-789");
+	}
+
 	// Roots Tests
 
 	@Test
@@ -1024,4 +1310,45 @@ public class McpSchemaTests {
 
 	}
 
+	// Progress Notification Tests
+
+	@Test
+	void testProgressNotificationWithMessage() throws Exception {
+		McpSchema.ProgressNotification notification = new McpSchema.ProgressNotification("progress-token-123", 0.5, 1.0,
+				"Processing file 1 of 2");
+
+		String value = mapper.writeValueAsString(notification);
+		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
+			.when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
+			.isObject()
+			.isEqualTo(
+					json("""
+							{"progressToken":"progress-token-123","progress":0.5,"total":1.0,"message":"Processing file 1 of 2"}"""));
+	}
+
+	@Test
+	void testProgressNotificationDeserialization() throws Exception {
+		McpSchema.ProgressNotification notification = mapper.readValue("""
+				{"progressToken":"token-456","progress":0.75,"total":1.0,"message":"Almost done"}""",
+				McpSchema.ProgressNotification.class);
+
+		assertThat(notification.progressToken()).isEqualTo("token-456");
+		assertThat(notification.progress()).isEqualTo(0.75);
+		assertThat(notification.total()).isEqualTo(1.0);
+		assertThat(notification.message()).isEqualTo("Almost done");
+	}
+
+	@Test
+	void testProgressNotificationWithoutMessage() throws Exception {
+		McpSchema.ProgressNotification notification = new McpSchema.ProgressNotification("progress-token-789", 0.25,
+				null, null);
+
+		String value = mapper.writeValueAsString(notification);
+		assertThatJson(value).when(Option.IGNORING_ARRAY_ORDER)
+			.when(Option.IGNORING_EXTRA_ARRAY_ITEMS)
+			.isObject()
+			.isEqualTo(json("""
+					{"progressToken":"progress-token-789","progress":0.25}"""));
+	}
+
 }