diff --git a/ask-llm.js b/ask-llm.js
index ad99b14..966d1fe 100755
--- a/ask-llm.js
+++ b/ask-llm.js
@@ -9,6 +9,29 @@ const LLM_STREAMING = process.env.LLM_STREAMING !== 'no';
 
 const LLM_DEBUG = process.env.LLM_DEBUG;
 
+/**
+ * Represents a chat message.
+ *
+ * @typedef {Object} Message
+ * @property {'system'|'user'|'assistant'} role
+ * @property {string} content
+ */
+
+/**
+ * A callback function to stream then completion.
+ *
+ * @callback CompletionHandler
+ * @param {string} text
+ * @returns {void}
+ */
+
+/**
+ * Generates a chat completion using a RESTful LLM API service.
+ *
+ * @param {Array<Message>} messages - List of chat messages.
+ * @param {CompletionHandler=} handler - An optional callback to stream the completion.
+ * @returns {Promise<string>} The completion generated by the LLM.
+ */
 const chat = async (messages, handler) => {
     const url = `${LLM_API_BASE_URL}/chat/completions`;
     const auth = LLM_API_KEY ? { 'Authorization': `Bearer ${LLM_API_KEY}` } : {};