Add support for audio content in prompts and tool results (#73)

Author: mattt

Sources/MCP/Server/Prompts.swift

@@ -64,6 +64,8 @@ public struct Prompt: Hashable, Codable, Sendable {
             case text(text: String)
             /// Image content
             case image(data: String, mimeType: String)
+            /// Audio content
+            case audio(data: String, mimeType: String)
             /// Embedded resource content
             case resource(uri: String, mimeType: String, text: String?, blob: String?)
 
@@ -82,6 +84,10 @@ public struct Prompt: Hashable, Codable, Sendable {
                     try container.encode("image", forKey: .type)
                     try container.encode(data, forKey: .data)
                     try container.encode(mimeType, forKey: .mimeType)
+                case .audio(let data, let mimeType):
+                    try container.encode("audio", forKey: .type)
+                    try container.encode(data, forKey: .data)
+                    try container.encode(mimeType, forKey: .mimeType)
                 case .resource(let uri, let mimeType, let text, let blob):
                     try container.encode("resource", forKey: .type)
                     try container.encode(uri, forKey: .uri)
@@ -103,6 +109,10 @@ public struct Prompt: Hashable, Codable, Sendable {
                     let data = try container.decode(String.self, forKey: .data)
                     let mimeType = try container.decode(String.self, forKey: .mimeType)
                     self = .image(data: data, mimeType: mimeType)
+                case "audio":
+                    let data = try container.decode(String.self, forKey: .data)
+                    let mimeType = try container.decode(String.self, forKey: .mimeType)
+                    self = .audio(data: data, mimeType: mimeType)
                 case "resource":
                     let uri = try container.decode(String.self, forKey: .uri)
                     let mimeType = try container.decode(String.self, forKey: .mimeType)
@@ -155,7 +165,7 @@ public enum ListPrompts: Method {
 
     public struct Parameters: NotRequired, Hashable, Codable, Sendable {
         public let cursor: String?
-        
+
         public init() {
             self.cursor = nil
         }

Sources/MCP/Server/Tools.swift

@@ -28,6 +28,8 @@ public struct Tool: Hashable, Codable, Sendable {
         case text(String)
         /// Image content
         case image(data: String, mimeType: String, metadata: [String: String]?)
+        /// Audio content
+        case audio(data: String, mimeType: String)
         /// Embedded resource content
         case resource(uri: String, mimeType: String, text: String?)
 
@@ -36,6 +38,7 @@ public struct Tool: Hashable, Codable, Sendable {
             case text
             case image
             case resource
+            case audio
             case uri
             case mimeType
             case data
@@ -56,6 +59,10 @@ public struct Tool: Hashable, Codable, Sendable {
                 let metadata = try container.decodeIfPresent(
                     [String: String].self, forKey: .metadata)
                 self = .image(data: data, mimeType: mimeType, metadata: metadata)
+            case "audio":
+                let data = try container.decode(String.self, forKey: .data)
+                let mimeType = try container.decode(String.self, forKey: .mimeType)
+                self = .audio(data: data, mimeType: mimeType)
             case "resource":
                 let uri = try container.decode(String.self, forKey: .uri)
                 let mimeType = try container.decode(String.self, forKey: .mimeType)
@@ -79,6 +86,10 @@ public struct Tool: Hashable, Codable, Sendable {
                 try container.encode(data, forKey: .data)
                 try container.encode(mimeType, forKey: .mimeType)
                 try container.encodeIfPresent(metadata, forKey: .metadata)
+            case .audio(let data, let mimeType):
+                try container.encode("audio", forKey: .type)
+                try container.encode(data, forKey: .data)
+                try container.encode(mimeType, forKey: .mimeType)
             case .resource(let uri, let mimeType, let text):
                 try container.encode("resource", forKey: .type)
                 try container.encode(uri, forKey: .uri)
@@ -120,7 +131,7 @@ public enum ListTools: Method {
 
     public struct Parameters: NotRequired, Hashable, Codable, Sendable {
         public let cursor: String?
-        
+
         public init() {
             self.cursor = nil
         }

Tests/MCPTests/PromptTests.swift

@@ -63,6 +63,18 @@ struct PromptTests {
             #expect(Bool(false), "Expected text content")
         }
 
+        // Test audio content
+        let audioContent = Prompt.Message.Content.audio(
+            data: "base64audiodata", mimeType: "audio/wav")
+        let audioData = try encoder.encode(audioContent)
+        let decodedAudio = try decoder.decode(Prompt.Message.Content.self, from: audioData)
+        if case .audio(let data, let mimeType) = decodedAudio {
+            #expect(data == "base64audiodata")
+            #expect(mimeType == "audio/wav")
+        } else {
+            #expect(Bool(false), "Expected audio content")
+        }
+
         // Test image content
         let imageContent = Prompt.Message.Content.image(data: "base64data", mimeType: "image/png")
         let imageData = try encoder.encode(imageContent)
@@ -142,7 +154,7 @@ struct PromptTests {
         let emptyParams = ListPrompts.Parameters()
         #expect(emptyParams.cursor == nil)
     }
-    
+
     @Test("ListPrompts request decoding with omitted params")
     func testListPromptsRequestDecodingWithOmittedParams() throws {
         // Test decoding when params field is omitted
@@ -157,7 +169,7 @@ struct PromptTests {
         #expect(decoded.id == "test-id")
         #expect(decoded.method == ListPrompts.name)
     }
-    
+
     @Test("ListPrompts request decoding with null params")
     func testListPromptsRequestDecodingWithNullParams() throws {
         // Test decoding when params field is null

Tests/MCPTests/ToolTests.swift

@@ -103,6 +103,26 @@ struct ToolTests {
         }
     }
 
+    @Test("Audio content encoding and decoding")
+    func testToolContentAudioEncoding() throws {
+        let content = Tool.Content.audio(
+            data: "base64audiodata",
+            mimeType: "audio/wav"
+        )
+        let encoder = JSONEncoder()
+        let decoder = JSONDecoder()
+
+        let data = try encoder.encode(content)
+        let decoded = try decoder.decode(Tool.Content.self, from: data)
+
+        if case .audio(let data, let mimeType) = decoded {
+            #expect(data == "base64audiodata")
+            #expect(mimeType == "audio/wav")
+        } else {
+            #expect(Bool(false), "Expected audio content")
+        }
+    }
+
     @Test("ListTools parameters validation")
     func testListToolsParameters() throws {
         let params = ListTools.Parameters(cursor: "next_page")