Add comprehensive README with usage examples

- Explains what the tool does and its key features
- Shows installation methods (releases and from source)
- Includes detailed usage examples with actual output
- Documents CLI options and table column meanings
- Explains cache pricing concept
- Adds development section with just commands

Author: tekacs

README.md

@@ -0,0 +1,167 @@
+# LLM Pricing
+
+A CLI tool to visualize OpenRouter model pricing in a clean, tabular format.
+
+## Features
+
+- 📊 **Tabular display** of model pricing per 1M tokens
+- 🔍 **Filter models** by name or provider (e.g., `anthropic`, `sonnet`)
+- 💰 **Cache pricing** support for models that offer it
+- 📝 **Verbose mode** showing all model details
+- 🌐 **Live data** fetched from OpenRouter API
+
+## Installation
+
+### From Releases
+
+Download the latest binary for your platform from the [releases page](https://github.com/tekacs/llm-pricing/releases).
+
+### From Source
+
+```bash
+git clone https://github.com/tekacs/llm-pricing.git
+cd llm-pricing
+cargo install --path .
+```
+
+## Usage
+
+### Basic Usage
+
+Show all models in a table format:
+
+```bash
+llm-pricing
+```
+
+```
+Model                                     | Input | Output | Cache Read | Cache Write
+------------------------------------------+-------+--------+------------+------------
+anthropic/claude-opus-4                   | 15.00 | 75.00  | 1.50       | 18.75      
+anthropic/claude-sonnet-4                 | 3.00  | 15.00  | 0.30       | 3.75       
+google/gemini-2.5-pro                     | 1.25  | 10.00  | N/A        | N/A        
+x-ai/grok-4                               | 3.00  | 15.00  | 0.75       | N/A        
+openai/gpt-4o                             | 2.50  | 10.00  | N/A        | N/A        
+...
+```
+
+### Filter by Provider
+
+Show only Anthropic models:
+
+```bash
+llm-pricing anthropic
+```
+
+```
+Model                                     | Input | Output | Cache Read | Cache Write
+------------------------------------------+-------+--------+------------+------------
+anthropic/claude-opus-4                   | 15.00 | 75.00  | 1.50       | 18.75      
+anthropic/claude-sonnet-4                 | 3.00  | 15.00  | 0.30       | 3.75       
+anthropic/claude-3.5-sonnet               | 3.00  | 15.00  | 0.30       | 3.75       
+anthropic/claude-3.5-haiku                | 0.80  | 4.00   | 0.08       | 1.00       
+anthropic/claude-3-opus                   | 15.00 | 75.00  | 1.50       | 18.75      
+...
+```
+
+### Filter by Model Name
+
+Show models containing "sonnet":
+
+```bash
+llm-pricing sonnet
+```
+
+```
+Model                                     | Input | Output | Cache Read | Cache Write
+------------------------------------------+-------+--------+------------+------------
+anthropic/claude-sonnet-4                 | 3.00  | 15.00  | 0.30       | 3.75       
+anthropic/claude-3.7-sonnet               | 3.00  | 15.00  | 0.30       | 3.75       
+anthropic/claude-3.5-sonnet               | 3.00  | 15.00  | 0.30       | 3.75       
+anthropic/claude-3-sonnet                 | 3.00  | 15.00  | 0.30       | 3.75       
+```
+
+### Verbose Output
+
+Get detailed information about models with the `-v` flag:
+
+```bash
+llm-pricing opus-4 -v
+```
+
+```
+=== ANTHROPIC ===
+
+Model: anthropic/claude-opus-4
+  Name: Anthropic: Claude Opus 4
+  Description: Claude Opus 4 is benchmarked as the world's best coding model, at time of release, 
+  bringing sustained performance on complex, long-running tasks and agent workflows. It sets new 
+  benchmarks in software engineering, achieving leading results on SWE-bench (72.5%) and 
+  Terminal-bench (43.2%).
+  Pricing:
+    Input: $15.00 per 1M tokens
+    Output: $75.00 per 1M tokens
+    Cache Read: $1.50 per 1M tokens
+    Cache Write: $18.75 per 1M tokens
+    Per Request: $0
+    Image: $0.024
+  Context Length: 200000 tokens
+  Modality: text+image->text
+  Tokenizer: Claude
+  Max Completion Tokens: 32000
+  Moderated: true
+```
+
+## Understanding the Output
+
+### Table Columns
+
+- **Model**: The model identifier used in API calls
+- **Input**: Cost per 1M input tokens (USD)
+- **Output**: Cost per 1M output tokens (USD)  
+- **Cache Read**: Cost per 1M tokens read from cache (when available)
+- **Cache Write**: Cost per 1M tokens written to cache (when available)
+
+### Cache Pricing
+
+Some providers (like Anthropic and xAI) offer caching to reduce costs on repeated content:
+
+- **Cache Read**: Much cheaper than regular input tokens (typically 10x less)
+- **Cache Write**: Slightly more expensive than input tokens (to build the cache)
+- **N/A**: Model doesn't support caching
+
+## CLI Options
+
+```bash
+llm-pricing [OPTIONS] [FILTER]
+
+Arguments:
+  [FILTER]  Filter models by name (e.g., 'anthropic/', 'sonnet')
+
+Options:
+  -v, --verbose  Show verbose output with all model information
+  -h, --help     Print help
+```
+
+## Development
+
+This project uses [just](https://github.com/casey/just) for task running:
+
+```bash
+# Show available tasks
+just
+
+# Build the project
+just build
+
+# Run with arguments
+just run anthropic -v
+
+# Format and lint
+just fmt
+just clippy
+```
+
+## License
+
+MIT License - see [LICENSE](LICENSE) for details.