Brex MCP Server

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

What’s New (0.3.2)

• Fix: Tools now include a permissive inputSchema in the tools list so clients like Claude Code properly display and allow calling tools. No behavior changes to handlers.

Installation

Claude Code

Claude Desktop

Add to your claude_desktop_config.json:

Manual Setup (Development)

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 (note: no date filter/expand on 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:

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

Note: Brex transactions endpoints (card and cash) do not support posted_at_start or expand. Retrieve transactions and, if needed, filter client-side by posted_at/posted_at_date.

Money & Units

All amounts from Brex are in cents. This server annotates money fields in tool outputs by default to prevent unit mistakes:

• amount_cents: integer (e.g., 100000)

• amount_dollars: number in dollars (e.g., 1000.0)

• amount_formatted: human-friendly string (e.g., "$1,000.00")

Example (expense purchased_amount):

Controls:

• format_amounts: "cents" | "dollars" | "both" (default: "both")

• include_formatted: boolean (default: true)

• include_summary: boolean (default: true) adds meta.summary totals/averages

Publishing

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

License

MIT — see LICENSE.