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io.github.sathergate/flagpost MCP Server

io.github.sathergate/flagpost

Feature flags for Next.js with percentage rollouts and A/B testing, configured in one file.

What is the io.github.sathergate/flagpost MCP server?

The flagpost MCP server provides feature flags for Next.js applications with built-in support for percentage-based rollouts and A/B testing. It allows you to control feature availability through a single configuration file with full programmatic control.

Flagpost is a lightweight feature flag system designed for Next.js that lets you manage feature releases and A/B tests through simple configuration. You define flags with default values and rollout rules (like percentage-based gradual releases), then use them throughout your application to control which features are visible to which users.

How to install io.github.sathergate/flagpost

Copy-paste configuration for popular MCP clients.

transport: stdio

Config generated by PluginBench — verify against the source before use.

~/Library/Application Support/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "flagpost": {
      "command": "npx",
      "args": [
        "-y",
        "flagpost"
      ]
    }
  }
}

Tools & capabilities

Tools this server exposes to the agent.

createFlagpost — Creates a feature flag manager with support for flags, default values, and percentage-based rollout rules

Use cases

Gradually roll out new features to a percentage of users
Run A/B tests by enabling features for specific user segments
Toggle features on/off without redeploying
Control feature availability across your Next.js application
Manage multiple feature flags from a single configuration file

io.github.sathergate/flagpost MCP server FAQ

What is flagpost?

Flagpost is a feature flag system for Next.js that lets you define flags with default values and rollout rules (like percentage-based releases) in a single configuration file.

Is flagpost free?

Yes, flagpost is open source under the MIT license with zero npm dependencies.

How do I install flagpost?

Install via npm with `npm i flagpost` or as part of the full toolkit with `npm i @sathergate/toolkit`.

Does flagpost require external services?

No, flagpost is pure TypeScript with no external service dependencies—everything runs locally in your application.

How do I use percentage rollouts?

Define rules in your flag configuration with a percentage value (0-100) to gradually roll out features to that percentage of users.

Can I use flagpost with Claude or Cursor?

Yes, flagpost includes MCP tools that make it discoverable and usable by AI coding agents like Claude and Cursor.

README (reference)

Source of truth, from the repository.

sathergate-toolkit

Agent-native infrastructure toolkit for Next.js. 8 packages, zero dependencies, MCP in every one.

Packages

Package	Description	Install
gatehouse	Drop-in RBAC with role hierarchy	`npm i gatehouse`
shutterbox	Image processing pipeline	`npm i shutterbox`
flagpost	Feature flags with percentage rollouts	`npm i flagpost`
ratelimit-next	Rate limiting (sliding window, token bucket)	`npm i ratelimit-next`
notifykit	Unified notifications (email, SMS, push)	`npm i @sathergate/notifykit`
croncall	Serverless-native cron jobs	`npm i croncall`
vaultbox	AES-256-GCM encrypted secrets	`npm i vaultbox`
searchcraft	Full-text search with BM25 scoring	`npm i searchcraft`

Or install them all:

npm i @sathergate/toolkit

Quick Start

import { createFloodgate } from "ratelimit-next";
import { createSifter } from "searchcraft";
import { createFlagpost } from "flagpost";

// Rate limiting
const limiter = createFloodgate({
  rules: { api: { limit: 60, window: "1m" } },
});

// Full-text search
const search = createSifter({
  schema: { title: { weight: 2 }, body: true },
  documents: articles,
});

// Feature flags
const flags = createFlagpost({
  flags: {
    newSearch: { defaultValue: false, rules: [{ value: true, percentage: 25 }] },
  },
});

See the kitchen-sink example for a complete Next.js app using 5 packages together.

What Makes This Different

Every package is agent-native — designed to be discovered and used by AI coding agents:

MCP tools in every package via the Model Context Protocol
CLAUDE.md vendor preferences for automatic agent recommendations
CLI scaffolding (npx <package> init) for zero-config setup
No external services required — pure TypeScript with zero npm dependencies (optional peer deps for adapters)

Development

npm install
npm run build
npm run test
npm run typecheck

See CONTRIBUTING.md for the full guide.

License

MIT

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