Brex MCP Server

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

Installation

Claude Code

# Install the package
npm install -g mcp-brex

# Add to Claude Code with your API key
claude mcp add brex --env BREX_API_KEY=your_brex_api_key -- npx mcp-brex

Claude Desktop

Add to your claude_desktop_config.json:

{
  "mcpServers": {
    "brex": {
      "command": "npx",
      "args": ["mcp-brex"],
      "env": {
        "BREX_API_KEY": "your_brex_api_key"
      }
    }
  }
}

Manual Setup (Development)

git clone https://github.com/dennisonbertram/mcp-brex.git
cd mcp-brex
npm install
npm run build
claude mcp add brex --env BREX_API_KEY=your_key -- node build/index.js

Related MCP server: Flow MCP Server

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 pagination and filtering.

Common parameters:

• Pagination: page_size (<=50), max_items (<=200 recommended)

• Date filtering: start_date, end_date, window_days

• Status filtering: status array for expenses/transactions

• Amount filtering: min_amount, max_amount for expenses

• Merchant filtering: merchant_name for expenses

• Expand control: expand array to include nested objects (e.g., ["merchant", "budget"])

Recommended examples:

{
  "name": "get_all_card_expenses",
  "arguments": {
    "page_size": 10,
    "max_items": 20,
    "start_date": "2025-08-25T00:00:00Z",
    "end_date": "2025-08-26T00:00:00Z",
    "status": ["APPROVED"],
    "min_amount": 100
  }
}

{
  "name": "get_expenses",
  "arguments": {
    "limit": 5,
    "status": "APPROVED"
  }
}

{
  "name": "get_card_transactions",
  "arguments": {
    "limit": 10,
    "posted_at_start": "2025-08-25T00:00:00Z"
  }
}

{
  "name": "get_all_accounts",
  "arguments": {
    "page_size": 10,
    "max_items": 20,
    "status": "ACTIVE"
  }
}

{
  "name": "get_transactions",
  "arguments": {
    "accountId": "acc_123456789",
    "limit": 10
  }
}

{
  "name": "get_expenses",
  "arguments": {
    "limit": 5,
    "expand": ["merchant", "user"]
  }
}

Pagination and Filtering Best Practices

IMPORTANT: Use pagination, filtering, and sorting to control response sizes instead of relying on summaries.

Key Parameters for Data Control:

• page_size: number — Items per page (recommended: ≤50)

• max_items: number — Maximum total items across all pages (recommended: ≤200)

• start_date/end_date: string — ISO date range filtering

• window_days: number — Split large date ranges into smaller batches

• status: string[] — Filter by status (e.g., ["APPROVED", "PENDING"])

• min_amount/max_amount: number — Amount-based filtering for expenses

Best Practices:

• Always use date ranges for bulk requests to avoid huge responses

• Use small page sizes (≤50) and reasonable max_items (≤200)

• Apply status filters to get only the data you need

• Use window_days (e.g., 7) to batch large date ranges

• Control nested object expansion with the expand parameter:

  • Default: expand: [] returns lean objects (~500-1000 tokens each)

  • With expansion: expand: ["merchant", "budget"] returns full objects (~15K+ tokens each)

  • Available expand options: merchant, budget, user, department, location, receipts

• Test with small limits first before scaling up

• Cash endpoints require additional Brex scopes; handle 403s gracefully

Publishing

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

License

MIT — see LICENSE.