Cobalt
Standalone unofficial fully-featured Whatsapp Web and Mobile API for Java and Kotlin
Cobalt MCP server is a development tooling MCP server that exposes WhatsApp Web client internals to AI coding assistants working on the Cobalt library. It enables AI agents to inspect the real WhatsApp client's behavior by launching a controlled browser instance, extracting runtime details like protobuf schemas, GraphQL operations, feature flags, and telemetry event definitions. The server helps developers and AI agents verify implementation parity between Cobalt and official WhatsApp clients, supporting reverse-engineering workflows for the Java/Kotlin WhatsApp API library.
Key Features
Use Cases
- 01Validating that Cobalt's protobuf models match the latest WhatsApp Web schema
- 02Extracting GraphQL operation definitions to keep client request models up-to-date
- 03Verifying feature-flag implementations against WhatsApp's ABProp configuration
- 04Comparing telemetry events generated by Cobalt with those from the official client
- 05Assisting AI coding agents in understanding WhatsApp protocol changes during Cobalt development
- 06Supporting reverse-engineering workflows by providing live client introspection
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Cobalt — FAQ
What is the Cobalt MCP server?+
The Cobalt MCP server is a specialized development tool that exposes WhatsApp Web client internals to AI coding assistants. It helps developers working on the Cobalt WhatsApp API library by providing live introspection of the real WhatsApp client's protobuf schemas, GraphQL operations, feature flags, and telemetry definitions.
How do I install the Cobalt MCP server?+
Navigate to tools/web/mcp-server in the Cobalt repository, run npm install, then npx playwright install chromium, followed by npm run build. Start the server with npm start from the same directory.
Which AI clients work with the Cobalt MCP server?+
The server is designed for MCP-compatible AI coding assistants like Claude Desktop and Cursor. It automatically integrates when the working directory is set to the Cobalt repository root.
Do I need API keys or WhatsApp credentials?+
No API keys are required. The server uses Playwright to control a Chromium browser instance that accesses the public WhatsApp Web client, extracting schema information from the loaded JavaScript runtime.
Is the Cobalt MCP server free to use?+
Yes, the MCP server is part of the open-source Cobalt project and is freely available under the MIT license. However, it is primarily a development tool for contributors working on Cobalt itself.
What are the prerequisites for running this MCP server?+
You need Node.js installed, the Cobalt repository cloned locally, and sufficient permissions to install Playwright's Chromium browser. The tool is specifically designed for Cobalt development workflows.
How do I install Cobalt?+
Open the source repository on GitHub and follow its README. Cobalt is a mcp server — MCP Agents Market links you directly to the official repo.
Is Cobalt free?+
Cobalt is an open-source project hosted on GitHub. Check the repository for its license and any usage requirements.