update readme

Author: fumito-ito

README.md

@@ -1,2 +1,65 @@
 # FunctionCalling-MacPaw-OpenAI
-Easy to use your Swift native functions for function calling with [MacPaw/OpenAI](https://github.com/MacPaw/OpenAI).
+
+This library simplifies the integration of the [FunctionCalling](https://github.com/fumito-ito/FunctionCalling) macro into [MacPaw/OpenAI](https://github.com/MacPaw/OpenAI). By using this library, you can directly generate `Tool` objects from Swift native functions, which can then be specified as FunctionCalling when invoking VertexAI.
+
+## Usage
+
+```swift
+
+import FunctionCalling
+import FunctionCalling_MacPaw_OpenAI
+import OpenAI
+
+// MARK: Declare the container and functions for the tools to be called from FunctionCalling.
+
+@FunctionCalling(service: .chatGPT)
+struct MyFunctionTools {
+    @CallableFunction
+    /// Get the current stock price for a given ticker symbol
+    ///
+    /// - Parameter: The stock ticker symbol, e.g. GOOG for Google Inc.
+    func getStockPrice(ticker: String) async throws -> String {
+        // code to return stock price of passed ticker
+    }
+}
+
+// MARK: You can directly pass the tools generated from objects to the model in ChatQuery.
+let query = ChatQuery(
+    model: .gpt3_5Turbo,
+    messages: [.init(role: .user, content: "who are you")],
+    tools: FunctionContainer().macPawOpenAITools
+)
+let result = try await openAI.chats(query: query)
+```
+
+## Installation
+
+### Swift Package Manager
+
+```
+let package = Package(
+    name: "MyPackage",
+    products: [...],
+    targets: [
+        .target(
+            "YouAppModule",
+            dependencies: [
+                .product(name: "FunctionCalling-MacPaw-OpenAI", package: "FunctionCalling-MacPaw-OpenAI")
+            ]
+        )
+    ],
+    dependencies: [
+        .package(url: "https://github.com/FunctionCalling/FunctionCalling-MacPaw-OpenAI", from: "0.1.0")
+    ]
+)
+```
+
+## Contributing
+
+Pull requests are welcome. For major changes, please open an issue first to discuss what you would like to change.
+
+Please make sure to update tests as appropriate.
+
+## License
+
+The MIT License