extend readme

Author: christian-bromann

libs/langchain-google/README.md

@@ -12,6 +12,37 @@ through the Google Cloud Platform environment it is running on.
 $ yarn add @langchain/google
 ```
 
+## Features
+
+This package provides:
+
+### Chat Models
+
+- **ChatGoogle** - Base Google chat model with automatic platform detection
+- **ChatVertexAI** - Google Vertex AI chat models (Gemini Pro, Gemini Pro Vision, etc.)
+- **ChatGoogleGenerativeAI** - Google AI Studio chat models (formerly @langchain/google-genai)
+
+### Language Models (LLMs)
+
+- **GoogleLLM** - Base Google LLM with automatic platform detection
+- **VertexAI** - Google Vertex AI language models
+
+### Embeddings
+
+- **GoogleEmbeddings** - Base Google embeddings with automatic platform detection
+- **VertexAIEmbeddings** - Google Vertex AI embeddings
+- **GoogleGenerativeAIEmbeddings** - Google AI Studio embeddings
+
+### Multimodal Support
+
+- Image inputs for vision models
+- Support for various image formats (base64, URLs, GCS paths)
+
+### Tool/Function Calling
+
+- Full support for Google's function calling capabilities
+- Tool binding and structured outputs
+
 ## Authorization
 
 Authorization is depending on the platform your are using this package in.
@@ -36,7 +67,7 @@ credentials from the first of the following that apply:
    logged in using `gcloud auth application-default login`, then the
    default credentials.
 
-## Browser
+### Browser
 
 Authorization is done through a Google Cloud Service Account.
 
@@ -52,3 +83,251 @@ credentials from the first of the following that apply:
    `GOOGLE_WEB_CREDENTIALS`
 5. The Service Account credentials that are saved directly into the
    `GOOGLE_VERTEX_AI_WEB_CREDENTIALS` (deprecated)
+
+## Usage Examples
+
+### Chat Models
+
+#### Basic Chat (Node.js)
+
+```typescript
+import { ChatGoogle } from "@langchain/google";
+
+const model = new ChatGoogle({
+  model: "gemini-1.5-pro",
+  temperature: 0.7,
+  apiKey: "your-api-key", // or set GOOGLE_API_KEY environment variable
+});
+
+const response = await model.invoke("Tell me a joke");
+console.log(response.content);
+```
+
+#### Vertex AI Chat (Node.js)
+
+```typescript
+import { ChatVertexAI } from "@langchain/google";
+
+const model = new ChatVertexAI({
+  model: "gemini-1.5-pro",
+  temperature: 0.7,
+  location: "us-central1", // optional
+  // Credentials will be automatically detected from environment
+});
+
+const response = await model.invoke("Explain quantum computing");
+console.log(response.content);
+```
+
+#### Multimodal Chat with Images
+
+```typescript
+import fs from "node:fs";
+import { ChatGoogle } from "@langchain/google";
+import { HumanMessage } from "@langchain/core/messages";
+import fs from "fs";
+
+const model = new ChatGoogle({
+  model: "gemini-1.5-pro-vision",
+});
+
+const image = fs.readFileSync("./image.jpg").toString("base64");
+const message = new HumanMessage({
+  content: [
+    {
+      type: "text",
+      text: "What's in this image?",
+    },
+    {
+      type: "image_url",
+      image_url: `data:image/jpeg;base64,${image}`,
+    },
+  ],
+});
+
+const response = await model.invoke([message]);
+console.log(response.content);
+```
+
+#### Web/Browser Usage
+
+```typescript
+import { ChatGoogle } from "@langchain/google/web";
+
+const model = new ChatGoogle({
+  model: "gemini-1.5-pro",
+  authOptions: {
+    credentials: JSON.parse(process.env.GOOGLE_WEB_CREDENTIALS),
+  },
+});
+
+const response = await model.invoke("Hello!");
+console.log(response.content);
+```
+
+### Language Models (LLMs)
+
+```typescript
+import { GoogleLLM } from "@langchain/google";
+
+const llm = new GoogleLLM({
+  model: "gemini-1.5-pro",
+  temperature: 0.7,
+  maxOutputTokens: 1000,
+});
+
+const response = await llm.invoke("Write a short story about AI");
+console.log(response);
+```
+
+### Embeddings
+
+#### Basic Embeddings
+
+```typescript
+import { GoogleEmbeddings } from "@langchain/google";
+
+const embeddings = new GoogleEmbeddings({
+  model: "text-embedding-004",
+});
+
+const vectors = await embeddings.embedDocuments([
+  "Hello world",
+  "How are you?",
+  "Goodbye!",
+]);
+
+console.log(vectors[0].length); // Vector dimension
+```
+
+#### Vertex AI Embeddings
+
+```typescript
+import { VertexAIEmbeddings } from "@langchain/google";
+
+const embeddings = new VertexAIEmbeddings({
+  model: "text-embedding-004",
+  location: "us-central1",
+});
+
+const vector = await embeddings.embedQuery("What is machine learning?");
+console.log(vector);
+```
+
+### Function/Tool Calling
+
+```typescript
+import { ChatGoogle } from "@langchain/google";
+import { z } from "zod";
+
+const model = new ChatGoogle({
+  model: "gemini-1.5-pro",
+});
+
+const weatherTool = {
+  name: "get_weather",
+  description: "Get the current weather for a location",
+  parameters: z.object({
+    location: z.string().describe("The city and state"),
+    unit: z.enum(["celsius", "fahrenheit"]).optional(),
+  }),
+};
+
+const modelWithTools = model.bindTools([weatherTool]);
+const response = await modelWithTools.invoke(
+  "What's the weather like in Paris?"
+);
+console.log(response.tool_calls);
+```
+
+### Streaming
+
+```typescript
+import { ChatGoogle } from "@langchain/google";
+
+const model = new ChatGoogle({
+  model: "gemini-1.5-pro",
+});
+
+const stream = await model.stream("Tell me a long story");
+for await (const chunk of stream) {
+  console.log(chunk.content);
+}
+```
+
+## Advanced Usage
+
+### Custom Authentication
+
+```typescript
+import { ChatGoogle } from "@langchain/google";
+
+const model = new ChatGoogle({
+  model: "gemini-1.5-pro",
+  authOptions: {
+    scopes: ["https://www.googleapis.com/auth/cloud-platform"],
+    credentials: {
+      // Your custom credentials
+    },
+  },
+});
+```
+
+### Batch Processing
+
+```typescript
+import { ChatGoogle } from "@langchain/google";
+
+const model = new ChatGoogle({
+  model: "gemini-1.5-pro",
+});
+
+const prompts = [
+  "Summarize this article...",
+  "Translate this text...",
+  "Answer this question...",
+];
+
+const responses = await model.batch(prompts);
+responses.forEach((response, index) => {
+  console.log(`Response ${index + 1}:`, response.content);
+});
+```
+
+## Troubleshooting
+
+### Common Issues
+
+1. **Authentication Errors**
+
+   - Ensure your API key or service account has the correct permissions
+   - Check that environment variables are set correctly
+
+2. **Rate Limiting**
+
+   - Implement exponential backoff
+   - Use batch processing for multiple requests
+
+3. **Model Not Found**
+
+   - Verify the model name is correct
+   - Ensure the model is available in your region
+
+4. **Browser CORS Issues**
+   - Ensure your domain is authorized in the Google Cloud Console
+   - Use appropriate CORS headers
+
+### Getting Help
+
+- [Google AI Documentation](https://ai.google.dev/docs)
+- [Vertex AI Documentation](https://cloud.google.com/vertex-ai/docs)
+- [LangChain.js Documentation](https://js.langchain.com/)
+- [GitHub Issues](https://github.com/langchain-ai/langchainjs/issues)
+
+## Contributing
+
+Contributions are welcome! Please see the [Contributing Guide](../../CONTRIBUTING.md) for details.
+
+## License
+
+This project is licensed under the MIT License.