Support audio content type in tools/call and prompts/get

client/inprocess_test.go

@@ -36,6 +36,11 @@ func TestInProcessMCPClient(t *testing.T) {
 					Type: "text",
 					Text: "Input parameter: " + request.Params.Arguments["parameter-1"].(string),
 				},
+				mcp.AudioContent{
+					Type:     "audio",
+					Data:     "base64-encoded-audio-data",
+					MIMEType: "audio/wav",
+				},
 			},
 		}, nil
 	})
@@ -77,6 +82,14 @@ func TestInProcessMCPClient(t *testing.T) {
 							Text: "Test prompt with arg1: " + request.Params.Arguments["arg1"],
 						},
 					},
+					{
+						Role: mcp.RoleUser,
+						Content: mcp.AudioContent{
+							Type:     "audio",
+							Data:     "base64-encoded-audio-data",
+							MIMEType: "audio/wav",
+						},
+					},
 				},
 			}, nil
 		},
@@ -192,8 +205,8 @@ func TestInProcessMCPClient(t *testing.T) {
 			t.Fatalf("CallTool failed: %v", err)
 		}
 
-		if len(result.Content) != 1 {
-			t.Errorf("Expected 1 content item, got %d", len(result.Content))
+		if len(result.Content) != 2 {
+			t.Errorf("Expected 2 content item, got %d", len(result.Content))
 		}
 	})
 
@@ -359,14 +372,17 @@ func TestInProcessMCPClient(t *testing.T) {
 
 		request := mcp.GetPromptRequest{}
 		request.Params.Name = "test-prompt"
+		request.Params.Arguments = map[string]string{
+			"arg1": "arg1 value",
+		}
 
 		result, err := client.GetPrompt(context.Background(), request)
 		if err != nil {
 			t.Errorf("GetPrompt failed: %v", err)
 		}
 
-		if len(result.Messages) != 1 {
-			t.Errorf("Expected 1 message, got %d", len(result.Messages))
+		if len(result.Messages) != 2 {
+			t.Errorf("Expected 2 message, got %d", len(result.Messages))
 		}
 	})
 

mcp/prompts.go

@@ -78,7 +78,7 @@ const (
 // resources from the MCP server.
 type PromptMessage struct {
 	Role    Role    `json:"role"`
-	Content Content `json:"content"` // Can be TextContent, ImageContent, or EmbeddedResource
+	Content Content `json:"content"` // Can be TextContent, ImageContent, AudioContent or EmbeddedResource
 }
 
 // PromptListChangedNotification is an optional notification from the server

mcp/tools.go

@@ -33,7 +33,7 @@ type ListToolsResult struct {
 // should be reported as an MCP error response.
 type CallToolResult struct {
 	Result
-	Content []Content `json:"content"` // Can be TextContent, ImageContent, or      EmbeddedResource
+	Content []Content `json:"content"` // Can be TextContent, ImageContent, AudioContent, or EmbeddedResource
 	// Whether the tool call ended in an error.
 	//
 	// If not set, this is assumed to be false (the call was successful).

mcp/types.go

@@ -656,7 +656,7 @@ type CreateMessageResult struct {
 // SamplingMessage describes a message issued to or received from an LLM API.
 type SamplingMessage struct {
 	Role    Role        `json:"role"`
-	Content interface{} `json:"content"` // Can be TextContent or ImageContent
+	Content interface{} `json:"content"` // Can be TextContent, ImageContent or AudioContent
 }
 
 type Annotations struct {
@@ -709,6 +709,19 @@ type ImageContent struct {
 
 func (ImageContent) isContent() {}
 
+// AudioContent represents the contents of audio, embedded into a prompt or tool call result.
+// It must have Type set to "audio".
+type AudioContent struct {
+	Annotated
+	Type string `json:"type"` // Must be "audio"
+	// The base64-encoded audio data.
+	Data string `json:"data"`
+	// The MIME type of the audio. Different providers may support different audio types.
+	MIMEType string `json:"mimeType"`
+}
+
+func (AudioContent) isContent() {}
+
 // EmbeddedResource represents the contents of a resource, embedded into a prompt or tool call result.
 //
 // It is up to the client how best to render embedded resources for the

mcp/utils.go

@@ -78,6 +78,11 @@ func AsImageContent(content interface{}) (*ImageContent, bool) {
 	return asType[ImageContent](content)
 }
 
+// AsAudioContent attempts to cast the given interface to AudioContent
+func AsAudioContent(content interface{}) (*AudioContent, bool) {
+	return asType[AudioContent](content)
+}
+
 // AsEmbeddedResource attempts to cast the given interface to EmbeddedResource
 func AsEmbeddedResource(content interface{}) (*EmbeddedResource, bool) {
 	return asType[EmbeddedResource](content)
@@ -208,7 +213,15 @@ func NewImageContent(data, mimeType string) ImageContent {
 	}
 }
 
-// NewEmbeddedResource
+// Helper function to create a new AudioContent
+func NewAudioContent(data, mimeType string) AudioContent {
+	return AudioContent{
+		Type:     "audio",
+		Data:     data,
+		MIMEType: mimeType,
+	}
+}
+
 // Helper function to create a new EmbeddedResource
 func NewEmbeddedResource(resource ResourceContents) EmbeddedResource {
 	return EmbeddedResource{
@@ -246,6 +259,23 @@ func NewToolResultImage(text, imageData, mimeType string) *CallToolResult {
 	}
 }
 
+// NewToolResultAudio creates a new CallToolResult with both text and audio content
+func NewToolResultAudio(text, imageData, mimeType string) *CallToolResult {
+	return &CallToolResult{
+		Content: []Content{
+			TextContent{
+				Type: "text",
+				Text: text,
+			},
+			AudioContent{
+				Type:     "audio",
+				Data:     imageData,
+				MIMEType: mimeType,
+			},
+		},
+	}
+}
+
 // NewToolResultResource creates a new CallToolResult with an embedded resource
 func NewToolResultResource(
 	text string,
@@ -423,6 +453,14 @@ func ParseContent(contentMap map[string]any) (Content, error) {
 		}
 		return NewImageContent(data, mimeType), nil
 
+	case "audio":
+		data := ExtractString(contentMap, "data")
+		mimeType := ExtractString(contentMap, "mimeType")
+		if data == "" || mimeType == "" {
+			return nil, fmt.Errorf("audio data or mimeType is missing")
+		}
+		return NewAudioContent(data, mimeType), nil
+
 	case "resource":
 		resourceMap := ExtractMap(contentMap, "resource")
 		if resourceMap == nil {