Functions are now working properly:

Sources/CleverBird/chat/ChatMessage.swift

@@ -37,22 +37,21 @@ public struct ChatMessage: Codable, Identifiable {
                 id: String? = nil,
                 functionCall: FunctionCall? = nil) throws {
 
-        // Validation: Name is required if role is function, and it should be the name of the function whose response is in the content.
-        if role == .function {
-            guard let functionCall = functionCall, let content = content, content.contains(functionCall.name) else {
-                throw CleverBirdError.invalidFunctionMessage
-            }
-        }
-
         // Validation: Content is required for all messages except assistant messages with function calls.
         if content == nil && !(role == .assistant && functionCall != nil) {
             throw CleverBirdError.invalidMessageContent
         }
 
         self.role = role
         self.content = content
-        self.functionCall = functionCall
         self.name = functionCall?.name
+        if role == .function {
+            // Attention: if the role is function I need to set the functionCall to nil, otherwise this will
+            // be encoded into the message which leads to an error.
+            self.functionCall = nil
+        } else {
+            self.functionCall = functionCall
+        }
 
         if let id = id {
             self.id = id
@@ -79,7 +78,8 @@ public struct ChatMessage: Codable, Identifiable {
     public func encode(to encoder: Encoder) throws {
         var container = encoder.container(keyedBy: CodingKeys.self)
         try container.encode(self.role, forKey: .role)
-        try container.encodeIfPresent(self.content, forKey: .content)
+        // The content field needs to be present even if it is nil, in this case encode it to Null
+        try container.encode(self.content, forKey: .content)
         try container.encodeIfPresent(self.functionCall, forKey: .functionCall)
         try container.encodeIfPresent(self.name, forKey: .name)
     }

Sources/CleverBird/chat/ChatThread.swift

@@ -92,7 +92,7 @@ public class ChatThread {
     }
 
     @discardableResult
-    func addFunctionResponse(_ content: String, for functionCall: FunctionCall) -> ChatThread {
+    public func addFunctionResponse(_ content: String, for functionCall: FunctionCall) -> ChatThread {
         do {
             let responseMessage = try ChatMessage(role: .function,
                                                   content: content,

Sources/CleverBird/chat/FunctionCall.swift

@@ -59,4 +59,10 @@ public struct FunctionCall: Codable {
         self.name = functionName
     }
 
+    public func encode(to encoder: Encoder) throws {
+        var container = encoder.container(keyedBy: CodingKeys.self)
+        try container.encode(self.name, forKey: .name)
+        let argumentsAsString = try String(data: JSONEncoder().encode(self.arguments), encoding: .utf8) ?? ""
+        try container.encode(argumentsAsString, forKey: .arguments)
+    }
 }