Quick start - Flex Documentation

Documentation Index

Fetch the complete documentation index at: /llms.txt

Use this file to discover all available pages before exploring further.

The Flex MCP server is hosted at https://mcp.withflex.com. Pick the client you use below — most paths take less than five minutes. The Claude.ai (web) flow is the most beginner-friendly; Claude Code is the best fit for developers; Cursor, Windsurf, and VS Code each have one-click install links from the Flex MCP landing page.

Claude.ai (per user)

Works on every paid Claude.ai plan (Pro, Max, Team, Enterprise) and only takes a sign-in.

1. Open Claude.ai connector settings

   Go to claude.ai → Settings → Connectors.

2. Add a custom connector

   Click Add custom connector, then paste the Flex MCP URL:

   https://mcp.withflex.com/api/mcp/oauth
   

   Give it a name (e.g. “Flex”) and click Add.

3. Sign in with your Flex account

   Claude will open a browser window to sign in. Use the email/password (or SSO) you use for the Flex Dashboard. Approve the access prompt.

4. Try it

   Back in Claude, ask:

   Use the Flex MCP to list my five most recent payment intents.

Claude will request approval to call a Flex tool the first time. Allow it once or “for this task,” and you’re connected.

🧪 Heads up — Claude.ai is OAuth, so test vs. live mode is set per call via an api_test_mode parameter the LLM passes to each tool. By default, read tools return live data and write tools require you to specify the mode. See Test mode for the full behavior.

Claude.ai (workspace admin)

If you’re on a Team or Enterprise plan, an admin can install the Flex connector once for the whole workspace instead of asking every member to add it individually.

1. Open admin Custom Connectors

   Follow Anthropic’s Custom Connectors guide to find the admin connector settings.

2. Add Flex

   Paste https://mcp.withflex.com/api/mcp/oauth as the connector URL, set the name to “Flex”, and save.

3. Members sign in on first use

   Each workspace member will be prompted to authenticate with their own Flex login the first time they use a Flex tool — there’s no shared service account.

Claude Code

For developers using Claude Code in the terminal.

• OAuth (recommended)
• API key

Run:

claude mcp add flex --transport http https://mcp.withflex.com/api/mcp/oauth

The first time you call a Flex tool, Claude Code will open a browser to sign in. Subsequent sessions reuse the token.

Create or copy an API key from the API keys page in your Flex Dashboard. Use an fsk_test_… key for experimentation.

claude mcp add flex --transport http https://mcp.withflex.com/api/mcp \
  --header "Authorization: Bearer fsk_YOUR_API_KEY"

🧪 Heads up — with the API key path, the key prefix encodes the mode: fsk_test_… always hits test data, fsk_… always hits live. There’s no per-call test-mode flag. See Authentication for details.

Confirm the connection from any prompt:

List the MCP tools available from Flex.

Other MCP clients

The Flex MCP works with any client that supports the Model Context Protocol. For Cursor, Windsurf, VS Code, and Claude Desktop, the easiest path is to visit mcp.withflex.com — pick your client and auth method, then click the one-click install link or copy the generated config. If you’re wiring up a client we don’t list explicitly, here’s what you need:

A minimal JSON config (the shape most clients accept) looks like:

{
  "mcpServers": {
    "flex": {
      "type": "http",
      "url": "https://mcp.withflex.com/api/mcp/oauth"
    }
  }
}

For the API key path, add a headers object with the Authorization bearer.Tested clients: Claude.ai · Claude Desktop · Claude Code · Cursor · Windsurf · VS Code (GitHub Copilot MCP). For each of these the Flex MCP landing page generates the exact config snippet.

Next steps

[**Try sample prompts**

Copy-paste prompts for support, reconciliation, refunds, and reporting.](https://docs.withflex.com/developer-guides/integration/mcp/tools)

[**Authentication & test mode**

How OAuth and API keys compare, and how to stay in test mode safely.](https://docs.withflex.com/developer-guides/integration/mcp/authentication)

[**Security best practices**

Scope your API keys and rotate credentials before going live.](https://docs.withflex.com/developer-guides/integration/mcp/security)