158 support resource links

CONTRIBUTING.md

@@ -80,6 +80,9 @@ See [How to Write a Git Commit Message](https://chris.beams.io/posts/git-commit/
 * Run `./gradlew assemble` to build the project and produce the corresponding artifacts.
 * Run `./gradlew test` to test the module and speed up development.
 * Run `./gradlew build` to build the project, which also runs all the tests.
+* Run `./gradlew allTests` to run all tests.
+
+*note*: when you change the data model, you might need to regenerate the .api files by running `./gradlew apiDump`.
 
 ## Contacting maintainers
 

kotlin-sdk-core/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/types.kt

@@ -975,19 +975,45 @@ public data class GetPromptRequest(
 }
 
 /**
- * Represents the content of a prompt message.
+ * The server's response content indicating the type of content.
  */
-@Serializable(with = PromptMessageContentPolymorphicSerializer::class)
-public sealed interface PromptMessageContent {
+public sealed interface ContentWithType {
     public val type: String
 }
 
 /**
- * Represents prompt message content that is either text, image or audio.
+ * Represents the content of a prompt message. Deprecated.
  */
-@Serializable(with = PromptMessageContentMultimodalPolymorphicSerializer::class)
+@Deprecated("For backwards compatibility; use ContentBlock instead", ReplaceWith("ContentBlock"))
+public sealed interface PromptMessageContent : ContentWithType
+
+/**
+ * Represents multimodal content of a prompt message. Deprecated.
+ */
+@Deprecated(
+    "For backwards compatibility; use CreateMessageResultContent or SamplingMessageContent instead",
+    ReplaceWith("CreateMessageResultContent"),
+)
 public sealed interface PromptMessageContentMultimodal : PromptMessageContent
 
+/**
+ * Represents the types of a ContentBlock
+ */
+@Serializable(with = ContentBlockPolymorphicSerializer::class)
+public sealed interface ContentBlock : PromptMessageContent
+
+/**
+ * Represents content for the CreateMessageResult
+ */
+@Serializable(with = CreateMessageResultContentMultimodalPolymorphicSerializer::class)
+public sealed interface CreateMessageResultContent : ContentWithType
+
+/**
+ * Represents content for the SamplingMessage
+ */
+@Serializable(with = SamplingMessageContentMultimodalPolymorphicSerializer::class)
+public sealed interface SamplingMessageContent : ContentWithType
+
 /**
  * Text provided to or from an LLM.
  */
@@ -1002,7 +1028,9 @@ public data class TextContent(
      * Optional annotations for the client.
      */
     val annotations: Annotations? = null,
-) : PromptMessageContentMultimodal {
+) : ContentBlock,
+    CreateMessageResultContent,
+    SamplingMessageContent {
     override val type: String = TYPE
 
     public companion object {
@@ -1029,7 +1057,9 @@ public data class ImageContent(
      * Optional annotations for the client.
      */
     val annotations: Annotations? = null,
-) : PromptMessageContentMultimodal {
+) : ContentBlock,
+    CreateMessageResultContent,
+    SamplingMessageContent {
     override val type: String = TYPE
 
     public companion object {
@@ -1056,19 +1086,80 @@ public data class AudioContent(
      * Optional annotations for the client.
      */
     val annotations: Annotations? = null,
-) : PromptMessageContentMultimodal {
+) : ContentBlock,
+    CreateMessageResultContent,
+    SamplingMessageContent {
     override val type: String = TYPE
 
     public companion object {
         public const val TYPE: String = "audio"
     }
 }
 
+/**
+ * A Resource Link provided to or from an LLM.
+ */
+@Serializable
+public data class ResourceLink(
+    /**
+     * A description of what this resource represents.
+     *
+     * This can be used by clients to improve the LLM’s understanding of available resources. It can be thought of like a “hint” to the model.
+     *
+     */
+    val description: String? = null,
+
+    /**
+     * Intended for programmatic or logical use, but used as a display name in past specs or fallback (if title isn’t present).
+     */
+    val name: String,
+
+    /**
+     * The size of the raw resource content, in bytes (i.e., before base64 encoding or any tokenization), if known.
+     *
+     * This can be used by Hosts to display file sizes and estimate context window usage.
+     *
+     */
+    val size: Long? = null,
+
+    /**
+     * Intended for UI and end-user contexts — optimized to be human-readable and easily understood, even by those unfamiliar with domain-specific terminology.
+     *
+     * If not provided, the name should be used for display (except for Tool, where annotations.title should be given precedence over using name, if present).
+     *
+     */
+    val title: String? = null,
+
+    /**
+     * The URI of this resource.
+     */
+    val uri: String,
+
+    /**
+     * The MIME type of this resource, if known.
+     */
+    val mimeType: String,
+
+    /**
+     * Optional annotations for the client.
+     */
+    val annotations: Annotations? = null,
+) : ContentBlock {
+    override val type: String = TYPE
+
+    public companion object {
+        public const val TYPE: String = "resource_link"
+    }
+}
+
 /**
  * Unknown content provided to or from an LLM.
  */
 @Serializable
-public data class UnknownContent(override val type: String) : PromptMessageContentMultimodal
+public data class UnknownContent(override val type: String) :
+    ContentBlock,
+    CreateMessageResultContent,
+    SamplingMessageContent
 
 /**
  * The contents of a resource, embedded into a prompt or tool call result.
@@ -1084,7 +1175,7 @@ public data class EmbeddedResource(
      * Optional annotations for the client.
      */
     val annotations: Annotations? = null,
-) : PromptMessageContent {
+) : ContentBlock {
     override val type: String = TYPE
 
     public companion object {
@@ -1134,7 +1225,7 @@ public data class Annotations(
  * Describes a message returned as part of a prompt.
  */
 @Serializable
-public data class PromptMessage(val role: Role, val content: PromptMessageContent)
+public data class PromptMessage(val role: Role, val content: ContentBlock)
 
 /**
  * The server's response to a prompts/get request from the client.
@@ -1286,7 +1377,7 @@ public class ListToolsResult(
  */
 @Serializable
 public sealed interface CallToolResultBase : ServerResult {
-    public val content: List<PromptMessageContent>
+    public val content: List<ContentBlock>
     public val structuredContent: JsonObject?
     public val isError: Boolean? get() = false
 }
@@ -1296,7 +1387,7 @@ public sealed interface CallToolResultBase : ServerResult {
  */
 @Serializable
 public class CallToolResult(
-    override val content: List<PromptMessageContent>,
+    override val content: List<ContentBlock>,
     override val structuredContent: JsonObject? = null,
     override val isError: Boolean? = false,
     override val _meta: JsonObject = EmptyJsonObject,
@@ -1307,7 +1398,7 @@ public class CallToolResult(
  */
 @Serializable
 public class CompatibilityCallToolResult(
-    override val content: List<PromptMessageContent>,
+    override val content: List<ContentBlock>,
     override val structuredContent: JsonObject? = null,
     override val isError: Boolean? = false,
     override val _meta: JsonObject = EmptyJsonObject,
@@ -1452,7 +1543,7 @@ public class ModelPreferences(
  * Describes a message issued to or received from an LLM API.
  */
 @Serializable
-public data class SamplingMessage(val role: Role, val content: PromptMessageContentMultimodal)
+public data class SamplingMessage(val role: Role, val content: SamplingMessageContent)
 
 /**
  * A request from the server to sample an LLM via the client.
@@ -1534,7 +1625,7 @@ public data class CreateMessageResult(
      */
     val stopReason: StopReason? = null,
     val role: Role,
-    val content: PromptMessageContentMultimodal,
+    val content: CreateMessageResultContent,
     override val _meta: JsonObject = EmptyJsonObject,
 ) : ClientResult
 

kotlin-sdk-core/src/commonMain/kotlin/io/modelcontextprotocol/kotlin/sdk/types.util.kt

@@ -81,21 +81,32 @@ internal object ReferencePolymorphicSerializer : JsonContentPolymorphicSerialize
         }
 }
 
-internal object PromptMessageContentPolymorphicSerializer :
-    JsonContentPolymorphicSerializer<PromptMessageContent>(PromptMessageContent::class) {
-    override fun selectDeserializer(element: JsonElement): DeserializationStrategy<PromptMessageContent> =
+internal object ContentBlockPolymorphicSerializer :
+    JsonContentPolymorphicSerializer<ContentBlock>(ContentBlock::class) {
+    override fun selectDeserializer(element: JsonElement): DeserializationStrategy<ContentBlock> =
         when (element.jsonObject.getValue("type").jsonPrimitive.content) {
             ImageContent.TYPE -> ImageContent.serializer()
             TextContent.TYPE -> TextContent.serializer()
             EmbeddedResource.TYPE -> EmbeddedResource.serializer()
             AudioContent.TYPE -> AudioContent.serializer()
+            ResourceLink.TYPE -> ResourceLink.serializer()
             else -> UnknownContent.serializer()
         }
 }
 
-internal object PromptMessageContentMultimodalPolymorphicSerializer :
-    JsonContentPolymorphicSerializer<PromptMessageContentMultimodal>(PromptMessageContentMultimodal::class) {
-    override fun selectDeserializer(element: JsonElement): DeserializationStrategy<PromptMessageContentMultimodal> =
+internal object CreateMessageResultContentMultimodalPolymorphicSerializer :
+    JsonContentPolymorphicSerializer<CreateMessageResultContent>(CreateMessageResultContent::class) {
+    override fun selectDeserializer(element: JsonElement): DeserializationStrategy<CreateMessageResultContent> =
+        when (element.jsonObject.getValue("type").jsonPrimitive.content) {
+            ImageContent.TYPE -> ImageContent.serializer()
+            TextContent.TYPE -> TextContent.serializer()
+            AudioContent.TYPE -> AudioContent.serializer()
+            else -> UnknownContent.serializer()
+        }
+}
+internal object SamplingMessageContentMultimodalPolymorphicSerializer :
+    JsonContentPolymorphicSerializer<SamplingMessageContent>(SamplingMessageContent::class) {
+    override fun selectDeserializer(element: JsonElement): DeserializationStrategy<SamplingMessageContent> =
         when (element.jsonObject.getValue("type").jsonPrimitive.content) {
             ImageContent.TYPE -> ImageContent.serializer()
             TextContent.TYPE -> TextContent.serializer()

kotlin-sdk-core/src/commonTest/kotlin/io/modelcontextprotocol/kotlin/sdk/RequestSerializerTest.kt

@@ -281,6 +281,57 @@ class RequestSerializerTest {
         assertEquals(buildJsonObject { put("result", "Legacy tool result") }, decoded.toolResult)
     }
 
+    // Only supported content types
+    @Test
+    fun `should not deserialize ResourceLink in CreateMessageResult`() {
+        val json = """{
+            "model": "test-model",
+            "role": "assistant", 
+            "content": {
+              "type": "resource_link",
+              "uri": "file:///project/src/main.rs",
+              "name": "main.rs",
+              "description": "Primary application entry point",
+              "mimeType": "text/x-rust"
+            },
+            "stopReason": "endTurn"
+        }"""
+
+        val decoded = McpJson.decodeFromString<RequestResult>(json)
+
+        assertIs<CreateMessageResult>(decoded)
+        assertEquals("test-model", decoded.model)
+        assertEquals(Role.assistant, decoded.role)
+        assertEquals(StopReason.EndTurn, decoded.stopReason)
+        assertIs<UnknownContent>(decoded.content)
+    }
+
+    // Only supported content types
+    @Test
+    fun `should not deserialize EmbeddedResource in CreateMessageResult`() {
+        val json = """{
+            "model": "test-model",
+            "role": "assistant", 
+            "content": {
+                "type": "resource", 
+                "resource": {
+                    "uri": "file:///test.txt",
+                    "mimeType": "text/plain",
+                    "text": "content"
+                }
+            },
+            "stopReason": "endTurn"
+        }"""
+
+        val decoded = McpJson.decodeFromString<RequestResult>(json)
+
+        assertIs<CreateMessageResult>(decoded)
+        assertEquals("test-model", decoded.model)
+        assertEquals(Role.assistant, decoded.role)
+        assertEquals(StopReason.EndTurn, decoded.stopReason)
+        assertIs<UnknownContent>(decoded.content)
+    }
+
     // Fallback Test
     @Test
     fun `should deserialize EmptyRequestResult for unknown result type`() {