About Flagbearer
Flagbearer provides feature-flag SDKs for applications across a range of languages and platforms. Its server SDKs download environment rules and evaluate flags locally.
Key features
- 01SDKs for web, mobile and server
- 02Local flag evaluation
- 03Shared evaluation test fixtures
- 04HTTP test servers for integration checks
Use cases
- 01Checking feature flags in an application
- 02Testing flag evaluation across SDKs
Configuration
Remote servers need no local install. Pick your client, then copy the config or install in one click.
https://mcp.flagbearer.devclaude mcp add --transport http dev-flagbearer-flagbearer https://mcp.flagbearer.dev{"mcpServers":{"dev-flagbearer-flagbearer":{"type":"http","url":"https://mcp.flagbearer.dev"}}}Open in Cursor{"servers":{"dev-flagbearer-flagbearer":{"type":"http","url":"https://mcp.flagbearer.dev"}}}Open in VS Code{"mcpServers":{"dev-flagbearer-flagbearer":{"type":"http","url":"https://mcp.flagbearer.dev"}}}{"mcpServers":{"dev-flagbearer-flagbearer":{"serverUrl":"https://mcp.flagbearer.dev"}}}Run commands in a terminal; paste JSON into the client’s MCP config and restart. Servers that need sign-in will prompt on first connect.
Tools
Details
From the project READMEFlagbearer SDKs
Official SDKs for Flagbearer feature flags. Server SDKs download an environment's rules once and check flags locally, so a flag check never waits on the network. Docs for each are at docs.flagbearer.dev.
| SDK | Directory | Package |
|---|---|---|
| Browser | js/web | @flagbearer/web (npm) |
| React Native | js/react-native | @flagbearer/react-native (npm) |
| iOS | swift | Swift Package Manager, from this repository |
| Android | android | dev.flagbearer:flagbearer-android (Maven Central) |
| Node.js | js/node | @flagbearer/node (npm) |
| Python | python | flagbearer-dev (PyPI) |
| Go | go | github.com/flagbearer-dev/sdks/go |
| Java and Kotlin | java | dev.flagbearer:flagbearer (Maven Central) |
| .NET | dotnet | Flagbearer (NuGet) |
| Ruby | ruby | flagbearer (RubyGems) |
| Rust | rust | flagbearer (crates.io) |
| C++ | cpp | CMake, from a git tag |
| PHP | flagbearer-dev/php-sdk | flagbearer/flagbearer (Packagist) |
The PHP SDK lives in its own repository, since Packagist publishes from a
repository's root. Go, C++ and iOS install straight from this repository's
tags. Swift Package Manager also reads a package only from a repository's root,
which is why Package.swift sits here beside the code in
swift/.
How the SDKs stay consistent
fixtures/evaluation.jsonholds rollout buckets and evaluation cases that every SDK's tests must reproduce exactly.testing/servers/has a small HTTP server per SDK with the same routes (GET /flags,GET /flush), which Flagbearer's integration tests run against the real backend.js/coreandjs/evaluatorare internal packages the JavaScript SDKs bundle.
Each SDK's README covers how to build, test and release it.
License
MIT
Comments
New to MCP?
From what the protocol is to installing your first server, these answers cover most first questions.
An open protocol that defines how AI applications connect to external tools and data in a uniform way. Clients talk to the model; MCP servers provide tools, resources and prompt templates. They exchange standard messages, so one server can be reused by many clients.