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An interactive REPL chat application with multi-provider support and tool calling. Perfect for exploring what AI can do when given real capabilities.

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Installation

cd samples/chatarang
dart pub get

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Quick Start

dart run

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Features

  • Multi-Provider: Switch between Google, OpenAI, and OpenRouter mid-conversation
  • Tool Calling: Built-in tools the AI can use to answer questions
  • Conversation Memory: Context persists across provider switches
  • Slash Commands: Control the app without leaving the chat

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Slash Commands

CommandArgumentsDescription
/helpShow available commands
/model[name]View current model or switch to new model
/models[filter]List available models (optionally filtered)
/toolsShow all available tools
/messagesDisplay full conversation history
/clearClear conversation and reset to system prompt
/exitQuit the application

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Model Switching

Switch providers or models at any time: 
You: /model openai:gpt-4o
Model set to: openai:gpt-4o

You: /model google:gemini-2.0-flash
Model set to: google:gemini-2.0-flash

You: /model anthropic
Model set to: anthropic
Model formats:
  • provider - Uses provider’s default model
  • provider:model - Specific model
  • provider/model - Alternative notation

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Filtering Models

You: /models gpt
openai:gpt-4o
openai:gpt-4o-mini
openai:gpt-4

You: /models gemini flash
google:gemini-2.0-flash
google:gemini-1.5-flash

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Viewing History

The /messages command shows the full conversation including tool interactions: 
You: /messages

SYSTEM: You are a helpful assistant...

You: What's the weather in Portland?

google:gemini-2.0-flash:
Tool.call: location-lookup({"location": "Portland, OR"})
Tool.result: location-lookup: {"postcode": "97240", ...}
Tool.call: weather({"zipcode": "97240"})
Tool.result: weather: {"FeelsLikeF": "53", ...}
The weather in Portland is currently 55°F with light rain.

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Built-in Tools

The AI can autonomously use these tools to answer your questions:

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current-time

Get the current time.
ParameterTypeRequiredDescription
(none)
Returns: ISO 8601 timestamp 
You: What time is it?
Tool.call: current-time({})
Tool.result: current-time: 2024-12-14T15:30:00.000Z
google:gemini-2.0-flash: It's currently 3:30 PM.

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current-date

Get the current date.
ParameterTypeRequiredDescription
(none)
Returns: ISO 8601 timestamp 
You: What's today's date?
Tool.call: current-date({})
Tool.result: current-date: 2024-12-14T00:00:00.000Z
google:gemini-2.0-flash: Today is December 14th, 2024.

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weather

Get weather information for a US zipcode.
ParameterTypeRequiredDescription
zipcodestringYesUS zipcode
Returns: JSON with current conditions, temperature, humidity, wind, UV index Data source: wttr.in API 
You: What's the weather in 97201?
Tool.call: weather({"zipcode": "97201"})
Tool.result: weather: {"current_condition": [{"FeelsLikeF": "53", "humidity": "89", ...}]}
google:gemini-2.0-flash: In Portland (97201), it's currently 55°F and feels like 53°F with 89% humidity.

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location-lookup

Get geographic data for any location query.
ParameterTypeRequiredDescription
locationstringYesLocation to search for
Returns: Array of location objects with coordinates, address details, place IDs Data source: OpenStreetMap Nominatim API 
You: Where is the Eiffel Tower?
Tool.call: location-lookup({"location": "Eiffel Tower, Paris"})
Tool.result: location-lookup: [{"lat": "48.8584", "lon": "2.2945", "display_name": "..."}]
google:gemini-2.0-flash: The Eiffel Tower is located at coordinates 48.8584°N, 2.2945°E in Paris, France.

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surf-web

Fetch the content of a web page.
ParameterTypeRequiredDescription
linkstringYesURL of the web page
Returns: HTML content of the page 
You: What's on example.com?
Tool.call: surf-web({"link": "https://example.com"})
Tool.result: surf-web: <!DOCTYPE html>...
google:gemini-2.0-flash: Example.com is a simple domain used for documentation examples...

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Multi-Step Tool Calling

Watch the AI chain tools together to solve complex questions: 
You: what's the weather at the moda center in portland, or?

Tool.call: location-lookup({
  "location": "Moda Center, Portland, OR"
})
Tool.result: { "postcode": "97240", ... }

Tool.call: weather({
  "zipcode": "97240"
})
Tool.result: { "FeelsLikeF": "53", "humidity": "89", ... }

google:gemini-2.0-flash: The weather at the Moda Center is currently
55°F with light rain. Wind from the south at 9 mph.
The AI figured out it needed to:
  1. Look up the Moda Center’s location to get a zipcode
  2. Use that zipcode to fetch the weather
  3. Synthesize the results into a natural response
That’s agentic behavior in action.

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Conversation Memory

Context persists across the entire session, including model switches: 
You: my name is chris
google:gemini-2.0-flash: Okay, Chris. How can I help you today?

You: /model openai:gpt-4o
Model set to: openai:gpt-4o

You: say my name
openai:gpt-4o: Your name is Chris. How can I assist you further?

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Environment Setup

Create a .env file in the chatarang directory or set environment variables: 
GEMINI_API_KEY=your_google_api_key
OPENAI_API_KEY=your_openai_api_key
OPENROUTER_API_KEY=your_openrouter_api_key

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Required Keys

ProviderEnvironment VariableRequired
GoogleGEMINI_API_KEYFor Google models
OpenAIOPENAI_API_KEYFor OpenAI models
OpenRouterOPENROUTER_API_KEYFor OpenRouter models
You only need keys for the providers you plan to use.

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Supported Providers

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Google (Gemini)

Default provider. Models include:
  • google:gemini-2.0-flash (default)
  • google:gemini-1.5-pro
  • google:gemini-1.5-flash

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OpenAI

GPT models:
  • openai:gpt-4o
  • openai:gpt-4o-mini
  • openai:gpt-4

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OpenRouter

Access to various models through OpenRouter:
  • openrouter:anthropic/claude-3-opus
  • openrouter:meta-llama/llama-3-70b
  • And many more

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Output Colors

Chatarang uses colors to distinguish message types:
ColorMeaning
BlueYour input (You:)
YellowModel response
MagentaTool calls
CyanTool results
RedSystem messages

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Sample Session

$ dart run
Welcome to Chatarang!
Type /help for available commands.
Found 42 models across 3 providers.

You: /models gemini
google:gemini-2.0-flash
google:gemini-1.5-pro
google:gemini-1.5-flash

You: What can you help me with?
google:gemini-2.0-flash: I can help you with a variety of tasks! I have access
to several tools that let me:

- Tell you the current time and date
- Look up weather for any US location
- Find geographic information about places
- Fetch and read web pages

What would you like to know?

You: What's the weather like in Seattle right now?
Tool.call: location-lookup({"location": "Seattle, WA"})
Tool.result: location-lookup: {"postcode": "98101", ...}
Tool.call: weather({"zipcode": "98101"})
Tool.result: weather: {"current_condition": [...]}
google:gemini-2.0-flash: In Seattle (98101), it's currently 48°F with
overcast skies and a light drizzle. Humidity is at 82%.

You: /model openai:gpt-4o
Model set to: openai:gpt-4o

You: What about Portland?
Tool.call: location-lookup({"location": "Portland, OR"})
Tool.result: location-lookup: {"postcode": "97201", ...}
Tool.call: weather({"zipcode": "97201"})
Tool.result: weather: {"current_condition": [...]}
openai:gpt-4o: Portland is a bit warmer at 52°F, also with overcast
conditions but no rain at the moment.

You: /exit
Goodbye!

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Adding Custom Tools

To add your own tools, edit lib/tools.dart: 
final myTool = Tool(
  name: 'my-tool',
  description: 'Description of what the tool does',
  inputSchema: JsonSchema.object({
    'param1': JsonSchema.string(description: 'First parameter'),
    'param2': JsonSchema.integer(description: 'Optional param'),
  }, required: ['param1']),
  onCall: (args) async {
    final param1 = args['param1'] as String;
    // Do something...
    return 'Result';
  },
);
Then add it to the tools list in the same file.