Brex MCP Server

A Model Context Protocol (MCP) server for the Brex API. Optimized for safe, small, read-only responses with projection and batching.

Quick Start

1. Install and build

npm install
npm run build

2. Run with stdio (example)

node build/index.js

3. Configure your MCP client to launch this command and pass env vars:

• BREX_API_KEY (required)
• BREX_API_URL default https://platform.brexapis.com

Resources

• brex://expenses | brex://expenses/{id} | brex://expenses/card | brex://expenses/card/{id}
• brex://budgets | brex://budgets/{id}
• brex://spend_limits | brex://spend_limits/{id}
• brex://budget_programs | brex://budget_programs/{id}
• brex://transactions/card/primary | brex://transactions/cash/{id}
• brex://docs/usage (compact usage guide for agents)

Notes:

• Resources accept ?summary_only=true&fields=id,status,... to control payload size.
• Expenses resources auto-expand merchant and budget for readability.

Tools (read-only unless noted)

• Budgets: get_budgets, get_budget
• Spend Limits: get_spend_limits, get_spend_limit
• Budget Programs: get_budget_programs, get_budget_program
• Expenses (single page): get_expenses
• Expenses (paginated): get_all_expenses, get_all_card_expenses
• Expense by ID: get_expense, get_card_expense
• Card Statements: get_card_statements_primary
• Transactions: get_card_transactions, get_cash_transactions
• Cash Statements: get_cash_account_statements
• Accounts: get_all_accounts, get_account_details
• Receipts (write): match_receipt, upload_receipt
• Updates (write): update_expense

How to call tools

Always send parameters under arguments (not input). Keep payloads small with summary_only and fields.

Common parameters:

• summary_only: boolean — compact projection; server auto-falls back if >24k tokens
• fields: string[] — dot-notation projection (e.g., purchased_amount.amount)
• Pagination: page_size (<=50), max_items (<=500 recommended)
• Date batching: start_date, end_date, window_days
• Thresholds: min_amount, max_amount

Recommended examples:

{
  "name": "get_all_card_expenses",
  "arguments": {
    "page_size": 50,
    "max_items": 200,
    "start_date": "2025-08-01T00:00:00Z",
    "end_date": "2025-08-18T00:00:00Z",
    "window_days": 7,
    "min_amount": 100,
    "summary_only": true,
    "fields": ["id","updated_at","status","purchased_amount.amount","purchased_amount.currency","merchant.raw_descriptor"]
  }
}

{
  "name": "get_expenses",
  "arguments": {
    "limit": 5,
    "status": "APPROVED",
    "summary_only": true,
    "fields": ["id","status","purchased_amount.amount","merchant.raw_descriptor"]
  }
}

{
  "name": "get_card_transactions",
  "arguments": {
    "limit": 10,
    "posted_at_start": "2025-08-01T00:00:00Z",
    "summary_only": true,
    "fields": ["id","posted_at","amount.amount","amount.currency","merchant.raw_descriptor"]
  }
}

Best practices:

• Always include summary_only: true and a focused fields list.
• Use date ranges and window_days for high-volume orgs.
• Keep page_size <= 50, prefer small max_items.
• Cash endpoints require additional Brex scopes; handle 403s gracefully.

Publishing

Only build/, README.md, and LICENSE are published.

License

MIT — see LICENSE.