FreeAgent MCP Server

A Model Context Protocol (MCP) server for the FreeAgent accounting API. Enables LLMs to manage contacts, invoices, estimates, bills, expenses, timeslips, projects, tasks, bank accounts, and more.

By my own admission, most of this project is vibe coded.

Features

• Broad FreeAgent coverage: contacts, invoices (incl. transitions and discounts), estimates (incl. transitions), bills, recurring invoices, price list items, expenses, timeslips, projects, tasks, bank accounts, bank transaction explanations, categories, company info, and users
• Intent-bundle tools: reconcile_bank_transaction, log_expense, and invoice_from_timeslips collapse multi-call sequences into single tool calls and resolve human-friendly hints (names, codes, references) to FreeAgent URLs server-side
• Optional tool-search mode (FREEAGENT_TOOL_SEARCH=true): collapses the tool catalog behind two meta-tools (freeagent_search_tools, freeagent_call_tool) so clients only pay the tool-definition token cost for tools they actually use
• MCP elicitation: create_invoice falls back to a form elicitation when contact is omitted (on clients that support it)
• Two deployment modes: local (stdio) or cloud (Vercel serverless via Streamable HTTP)
• OAuth 2.0: stateless JWT-based auth for serverless, or direct token for local use
• Tool annotations: readOnlyHint, destructiveHint, idempotentHint, openWorldHint on every tool
• Zod validation: strict input schemas with .describe() on all fields
• Dual response formats: Markdown (human-readable) or JSON (structured)
• Pagination: proper header parsing with x-total-count and Link headers
• Rate limit handling: clear error messages with retry-after guidance
• Sandbox support: test safely against FreeAgent's sandbox environment

Deployment Options

Local (stdio) - for Claude Desktop

1. Install and build:

   bun install
   bun run build
   

2. Set environment variables:

   export FREEAGENT_ACCESS_TOKEN="your_access_token"
   export FREEAGENT_USE_SANDBOX="true"  # optional
   

3. Add to Claude Desktop config (~/Library/Application Support/Claude/claude_desktop_config.json):

   {
     "mcpServers": {
       "freeagent": {
         "command": "node",
         "args": ["/path/to/freeagent-mcp-server/dist/index.js"],
         "env": {
           "FREEAGENT_ACCESS_TOKEN": "your_token",
           "FREEAGENT_USE_SANDBOX": "true"
         }
       }
     }
   }
   

Vercel (Streamable HTTP) - for cloud access

See VERCEL_DEPLOYMENT.md for full instructions. Key points:

• Uses StreamableHTTPServerTransport in stateless mode (no sessions)
• OAuth 2.0 with PKCE via JWT-encoded tokens (no database needed)
• Handles POST (tool calls), GET (SSE streaming), and DELETE (returns 405 - stateless)
• Set PRODUCTION_URL env var for stable OAuth callback URLs

Required env vars: FREEAGENT_CLIENT_ID, FREEAGENT_CLIENT_SECRET

Tool-Search Mode (optional)

By default the server registers every catalog tool directly, which makes all ~50 tool definitions part of the MCP client's tools/list response. For clients with many connected MCP servers — where tool-definition tokens add up quickly — set:

export FREEAGENT_TOOL_SEARCH=true

In this mode the server exposes only two meta-tools:

Tool	Purpose
freeagent_search_tools	Search the catalog and return JSONSchema for matching tools. Query forms: select:name1,name2 for direct lookup, +required optional for scored search with required keywords, or plain keywords for a ranked search.
freeagent_call_tool	Invoke any catalog tool by name with validated arguments ({ name, arguments }). Pair with search_tools to discover schemas on demand.

The full catalog is still reachable — it's just loaded on demand. This mirrors the deferred-loading pattern used by Claude Code's internal ToolSearch.

Available Tools

See TOOLS.md for per-tool parameters and examples. Summary:

Contacts

Tool	Description	Read-only
freeagent_list_contacts	List contacts with pagination and sorting	Yes
freeagent_get_contact	Get contact details by ID	Yes
freeagent_create_contact	Create a new contact	No

Invoices

Tool	Description	Read-only
freeagent_list_invoices	List invoices with status/contact/project filters	Yes
freeagent_get_invoice	Get invoice details (renders computed discount amount)	Yes
freeagent_create_invoice	Create a draft invoice (supports discount_percent; elicits contact if omitted)	No
freeagent_transition_invoice	mark_as_sent / mark_as_cancelled / mark_as_draft / mark_as_scheduled / convert_to_credit_note	No
freeagent_invoice_from_timeslips	Intent bundle: draft an invoice from a contact's unbilled timeslips	No

Estimates

Tool	Description	Read-only
freeagent_list_estimates	List estimates with status/contact/project filters	Yes
freeagent_get_estimate	Get estimate details (renders computed discount amount)	Yes
freeagent_create_estimate	Draft an estimate (supports discount_percent)	No
freeagent_transition_estimate	mark_as_sent / mark_as_approved / mark_as_rejected / mark_as_cancelled / mark_as_draft / convert_to_invoice	No

Bills

Tool	Description	Read-only
freeagent_list_bills	List supplier bills with filters	Yes
freeagent_get_bill	Get bill details	Yes
freeagent_create_bill	Record a supplier bill	No

Recurring Invoices

Tool	Description	Read-only
freeagent_list_recurring_invoices	List recurring invoice templates	Yes
freeagent_get_recurring_invoice	Get template details	Yes

Price List Items

Tool	Description	Read-only
freeagent_list_price_list_items	List catalog items	Yes
freeagent_get_price_list_item	Get catalog item details	Yes
freeagent_create_price_list_item	Add a catalog item	No

Expenses

Tool	Description	Read-only
freeagent_list_expenses	List expenses with date/view filters	Yes
freeagent_get_expense	Get expense details (inc. mileage info)	Yes
freeagent_create_expense	Create expense or mileage claim (with attachments)	No
freeagent_update_expense	Update an existing expense	No
freeagent_log_expense	Intent bundle: log a regular expense with a positive amount + kind enum	No

Timeslips

Tool	Description	Read-only
freeagent_list_timeslips	List time entries with filters	Yes
freeagent_get_timeslip	Get timeslip details	Yes
freeagent_create_timeslip	Create a time entry	No
freeagent_update_timeslip	Update a timeslip (incl. billed_on_invoice)	No

Bank Accounts & Transactions

Tool	Description	Read-only
freeagent_list_bank_accounts	List all bank accounts	Yes
freeagent_get_bank_account	Get bank account details	Yes
freeagent_list_bank_transactions	List transactions for an account	Yes
freeagent_get_bank_transaction	Get bank transaction details	Yes
freeagent_list_bank_transaction_explanations	List transaction explanations	Yes
freeagent_get_bank_transaction_explanation	Get explanation details	Yes
freeagent_create_bank_transaction_explanation	Explain/categorize a bank transaction	No
freeagent_update_bank_transaction_explanation	Update a transaction explanation	No
freeagent_reconcile_bank_transaction	Intent bundle: explain a transaction with a category name / invoice ref / bill ref	No

Projects & Tasks

Tool	Description	Read-only
freeagent_list_projects	List projects with status/contact filters	Yes
freeagent_get_project	Get project details	Yes
freeagent_create_project	Create a new project	No
freeagent_list_tasks	List tasks with project/status filters	Yes
freeagent_get_task	Get task details	Yes
freeagent_create_task	Create a task within a project	No

Categories, Company & Users

Tool	Description	Read-only
freeagent_list_categories	List accounting categories	Yes
freeagent_get_category	Get category by nominal code	Yes
freeagent_get_company	Get company information	Yes
freeagent_list_users	List all users	Yes

Development

Prerequisites

• Bun (used for package management and running scripts)
• Node.js 22.x

Setup

bun install

Scripts

Command	Description
bun run build	Compile TypeScript
bun run dev	Watch mode (auto-recompile)
bun run start	Run the compiled server
bun run lint	Run ESLint
bun run test	Run tests
bun run test:watch	Run tests in watch mode
bun run test:coverage	Run tests with coverage

Project Structure

freeagent-mcp-server/
├── src/
│   ├── index.ts                       # Stdio server entry point
│   ├── constants.ts                   # Configuration constants & shared utilities
│   ├── types.ts                       # TypeScript type definitions
│   ├── schemas/
│   │   ├── index.ts                   # Zod validation schemas for all tools
│   │   ├── projects.ts                # Project-specific schemas
│   │   └── schemas.test.ts            # Schema validation tests
│   ├── services/
│   │   ├── api-client.ts              # FreeAgent API client (Axios)
│   │   ├── api-client.test.ts         # API client tests
│   │   ├── formatter.ts               # Response formatting utilities (incl. discount amount helper)
│   │   ├── formatter.test.ts          # Formatter tests
│   │   ├── resolvers.ts               # Shared resolvers (category / user / contact / bill hints → URLs)
│   │   ├── oauth-jwt.ts               # JWT-based OAuth provider (Vercel)
│   │   └── freeagent-auth.ts          # Token validation
│   └── tools/
│       ├── register.ts                # Shared tool definitions, registration, ToolContext (elicitation)
│       ├── contacts.ts                # Contact CRUD
│       ├── invoices.ts                # Invoice management (incl. elicitation fallback)
│       ├── transition-invoice.ts      # Invoice lifecycle transitions
│       ├── invoice-from-timeslips.ts  # Intent bundle: draft an invoice from unbilled time
│       ├── estimates.ts               # Estimates + transition_estimate
│       ├── bills.ts                   # Supplier bills
│       ├── recurring-invoices.ts      # Recurring invoice templates (read-only)
│       ├── price-list-items.ts        # Catalog items
│       ├── expenses.ts                # Expense & mileage tracking
│       ├── log-expense.ts             # Intent bundle: positive-amount expense logging
│       ├── timeslips.ts               # Time tracking (incl. update_timeslip)
│       ├── bank-accounts.ts           # Bank accounts & transactions
│       ├── bank-transactions.ts       # Transaction explanations
│       ├── reconcile.ts               # Intent bundle: reconcile a transaction in one call
│       ├── projects.ts                # Project management
│       ├── tasks.ts                   # Task management
│       ├── categories.ts              # Accounting categories
│       └── company.ts                 # Company info & users
├── api/
│   └── index.ts              # Vercel serverless entry point
├── .github/
│   └── workflows/
│       └── ci.yml            # GitHub Actions CI (lint, test, build)
├── eslint.config.js          # ESLint flat config
├── vitest.config.ts          # Vitest configuration
├── vercel.json               # Vercel deployment config
├── package.json
└── tsconfig.json

CI

GitHub Actions runs on every push to main and on pull requests:

• Lint: ESLint with TypeScript rules
• Test: Vitest unit tests (no external API calls)
• Build: TypeScript compilation check

Rate Limiting

Environment	Limit
Production	15 requests / 60 seconds
Sandbox	5 requests / 60 seconds

The server returns clear error messages with retry-after timing when rate limited.

Error Handling

All tool handlers return structured errors via { isError: true, content: [...] } (never thrown exceptions). Error messages are designed for LLM consumption with actionable guidance:

Status	Meaning
401	Token expired - refresh OAuth token
403	Insufficient permissions
404	Resource not found or deleted
422	Validation error with field-level details
429	Rate limited - retry after N seconds

Security

• Access tokens are never logged or committed
• JWT tokens use HS256 signing with configurable secret
• PKCE is used for the OAuth authorization flow
• Strict Zod schemas reject unexpected input fields
• Bearer auth middleware protects all MCP endpoints

License

MIT

Links

• FreeAgent API Docs
• MCP Specification
• FreeAgent Developer Dashboard