Update ADK doc according to issue #1292 - 4 - Prompt Optimizer

docs/agents/prompt-optimization.md

@@ -0,0 +1,59 @@
+---
+title: Simple Prompt Optimizer
+---
+
+The Simple Prompt Optimizer is a tool that helps you iteratively improve the system prompt of an agent.
+
+## How it works
+
+The optimizer uses a large language model (LLM), by default `gemini-1.5-flash`, to critique and rewrite the agent's prompt. This process is guided by evaluation scores from a `Sampler` that you provide. The optimizer runs for a specified number of iterations, and in each iteration, it generates a new prompt, evaluates it, and retains the version that performs the best.
+
+## Usage
+
+To use the `SimplePromptOptimizer`, you need to:
+
+1.  Define an `Agent` and a `Sampler`. The `Sampler` is used for evaluation and should contain your evaluation dataset.
+2.  Configure the `SimplePromptOptimizerConfig` with the desired number of iterations (`num_iterations`) and batch size (`batch_size`).
+3.  Instantiate the `SimplePromptOptimizer` with the configuration.
+4.  Call the `optimize()` method with your agent and sampler.
+
+Here is an example of how to use the `SimplePromptOptimizer`:
+
+```python
+from google.adk.agents import Agent
+from google.adk.optimization import SimplePromptOptimizer, SimplePromptOptimizerConfig
+from google.adk.optimization import Sampler
+
+# 1. Define an Agent and a Sampler
+my_agent = Agent(
+    instruction="You are a helpful assistant.",
+    # ... other agent configuration
+)
+
+my_sampler = Sampler(
+    # ... sampler configuration
+)
+
+# 2. Configure the SimplePromptOptimizer
+optimizer_config = SimplePromptOptimizerConfig(
+    num_iterations=10,
+    batch_size=5,
+)
+
+# 3. Instantiate the optimizer
+optimizer = SimplePromptOptimizer(config=optimizer_config)
+
+# 4. Run the optimization
+optimizer_result = await optimizer.optimize(
+    initial_agent=my_agent,
+    sampler=my_sampler,
+)
+
+# The best performing agent is available in the result
+best_agent = optimizer_result.optimized_agents[0].optimized_agent
+```
+
+## Key Classes
+
+*   `SimplePromptOptimizer`: The main class that runs the optimization loop.
+*   `SimplePromptOptimizerConfig`: The configuration class for the `SimplePromptOptimizer`, allowing you to set the number of iterations, batch size, and the optimizer model.