Validate ResourceLink required fields

Author: pragnyanramtha

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

@@ -5019,6 +5019,40 @@ public record ResourceLink( // @formatter:off
 		@JsonProperty("annotations") Annotations annotations,
 		@JsonProperty("_meta") Map<String, Object> meta) implements Content, ResourceContent { // @formatter:on
 
+		public ResourceLink {
+			Assert.notNull(uri, "uri must not be null");
+			Assert.notNull(name, "name must not be null");
+		}
+
+		@JsonCreator
+		static ResourceLink fromJson(@JsonProperty("name") String name, @JsonProperty("title") String title,
+				@JsonProperty("uri") String uri, @JsonProperty("description") String description,
+				@JsonProperty("mimeType") String mimeType, @JsonProperty("size") Long size,
+				@JsonProperty("annotations") Annotations annotations, @JsonProperty("_meta") Map<String, Object> meta) {
+			if (name == null || uri == null) {
+				List<String> missing = new ArrayList<>();
+				if (name == null) {
+					missing.add("name -> ''");
+					name = "";
+				}
+				if (uri == null) {
+					missing.add("uri -> ''");
+					uri = "";
+				}
+				logger.warn("ResourceLink: missing required fields during deserialization: {}",
+						String.join(", ", missing));
+			}
+			return new ResourceLink(name, title, uri, description, mimeType, size, annotations, meta);
+		}
+
+		public static Builder builder(String uri, String name) {
+			return new Builder(uri, name);
+		}
+
+		/**
+		 * @deprecated Use {@link #builder(String, String)} instead.
+		 */
+		@Deprecated
 		public static Builder builder() {
 			return new Builder();
 		}
@@ -5041,6 +5075,24 @@ public static class Builder {
 
 			private Map<String, Object> meta;
 
+			/**
+			 * @deprecated Use {@link ResourceLink#builder(String, String)} instead.
+			 */
+			@Deprecated
+			public Builder() {
+			}
+
+			private Builder(String uri, String name) {
+				Assert.hasText(uri, "uri must not be empty");
+				Assert.hasText(name, "name must not be empty");
+				this.uri = uri;
+				this.name = name;
+			}
+
+			/**
+			 * @deprecated Use {@link ResourceLink#builder(String, String)} instead.
+			 */
+			@Deprecated
 			public Builder name(String name) {
 				this.name = name;
 				return this;
@@ -5051,6 +5103,10 @@ public Builder title(String title) {
 				return this;
 			}
 
+			/**
+			 * @deprecated Use {@link ResourceLink#builder(String, String)} instead.
+			 */
+			@Deprecated
 			public Builder uri(String uri) {
 				this.uri = uri;
 				return this;

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

@@ -228,10 +228,8 @@ void testEmbeddedResourceWithBlobContentsDeserialization() throws Exception {
 
 	@Test
 	void testResourceLink() throws Exception {
-		McpSchema.ResourceLink resourceLink = McpSchema.ResourceLink.builder()
-			.name("main.rs")
+		McpSchema.ResourceLink resourceLink = McpSchema.ResourceLink.builder("file:///project/src/main.rs", "main.rs")
 			.title("Main file")
-			.uri("file:///project/src/main.rs")
 			.description("Primary application entry point")
 			.mimeType("text/x-rust")
 			.meta(Map.of("metaKey", "metaValue"))
@@ -261,6 +259,44 @@ void testResourceLinkDeserialization() throws Exception {
 		assertThat(resourceLink.meta()).containsEntry("metaKey", "metaValue");
 	}
 
+	@Test
+	void testResourceLinkRejectsNullName() {
+		assertThatThrownBy(() -> new McpSchema.ResourceLink(null, null, "file:///project/src/main.rs", null, null, null,
+				null, null))
+			.isInstanceOf(IllegalArgumentException.class)
+			.hasMessage("name must not be null");
+	}
+
+	@Test
+	void testResourceLinkRejectsNullUri() {
+		assertThatThrownBy(() -> new McpSchema.ResourceLink("main.rs", null, null, null, null, null, null, null))
+			.isInstanceOf(IllegalArgumentException.class)
+			.hasMessage("uri must not be null");
+	}
+
+	@Test
+	void testResourceLinkDeserializationWithMissingRequiredFields() throws Exception {
+		McpSchema.ResourceLink resourceLink = JSON_MAPPER.readValue("""
+				{"type":"resource_link","description":"Primary application entry point"}""",
+				McpSchema.ResourceLink.class);
+
+		assertThat(resourceLink).isNotNull();
+		assertThat(resourceLink.name()).isEmpty();
+		assertThat(resourceLink.uri()).isEmpty();
+		assertThat(resourceLink.description()).isEqualTo("Primary application entry point");
+	}
+
+	@Test
+	void testResourceLinkUnknownFieldsIgnored() throws Exception {
+		McpSchema.ResourceLink resourceLink = JSON_MAPPER.readValue(
+				"""
+						{"type":"resource_link","name":"main.rs","uri":"file:///project/src/main.rs","futureField":"ignored"}""",
+				McpSchema.ResourceLink.class);
+
+		assertThat(resourceLink.name()).isEqualTo("main.rs");
+		assertThat(resourceLink.uri()).isEqualTo("file:///project/src/main.rs");
+	}
+
 	// JSON-RPC Message Types Tests
 
 	@Test