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Announcing StackOne Defender: leading open-source prompt injection guard for your agent • Read More →
StackOne's FreeAgent MCP server gives AI agents 105 ready-to-use actions for FreeAgent — with built-in authentication, security, governance, token efficiency, and high tool-calling accuracy.
Coverage
Create, read, update, and delete across FreeAgent — and extend your agent's capabilities with custom actions.
Authentication
Per-user OAuth in one call. Your FreeAgent MCP server gets session-scoped tokens with zero credentials stored on your infra.
Agent Auth →Security
Every FreeAgent tool response scanned for prompt injection in milliseconds — 88.7% accuracy, all running on CPU.
Prompt Injection Defense →Performance
Free up to 96% of your agent's context window to enhance reasoning and reduce cost, on every FreeAgent call.
Tools Discovery →A FreeAgent MCP server lets AI agents read and write FreeAgent data through the Model Context Protocol — Anthropic's open standard for connecting LLMs to external tools. StackOne's FreeAgent MCP server ships with 105 pre-built actions, fully extensible via the Connector Builder — plus managed authentication, prompt injection defense, and optimized agent context. Connect it from MCP clients like Claude Desktop, Claude Code, Cursor, Goose, and VS Code, or from agent frameworks like OpenAI Agents SDK, LangChain, and Vercel AI SDK.
Every action from FreeAgent's API, ready for your agent. Create, read, update, and delete — scoped to exactly what you need.
Create a new bank account in FreeAgent with a specified type, currency, and opening balance
Retrieve all bank accounts linked to the FreeAgent company, filterable by account type
Retrieve a single bank account by its unique ID
Update an existing bank account's name, bank name, or personal flag
Permanently delete a bank account from FreeAgent
Retrieve all bank transactions for a specific bank account, with optional date, status, and upload filters
Retrieve a single bank transaction by its unique ID, including full explanation details
Permanently delete a bank transaction from FreeAgent
Create a new bill (accounts payable) in FreeAgent with one or more line items
Retrieve all bills (accounts payable) with optional filtering by contact, project, payment status, and date range
Retrieve a single bill by ID, including bill items, payment status, and attachment details
Update an existing bill's details, line items, or add/remove bill items
Permanently delete a bill and its associated bill items from FreeAgent
Create a custom accounting category in FreeAgent
Retrieve a single accounting category by its nominal code
Update a custom accounting category by nominal code
Delete a user-created accounting category by nominal code
Create a new contact (client or supplier) in FreeAgent
Retrieve all contacts (clients and suppliers) with optional filtering by type, status, and activity
Retrieve a single contact by ID with full profile, balance, and CIS details
Update an existing contact's details, address, invoice settings, or CIS configuration
Permanently delete a contact from FreeAgent
Create a new credit note in Draft status for a specified contact
Retrieve all credit notes with optional filtering by contact, project, status, and date
Retrieve a single credit note by ID with full line item and payment details
Update an existing credit note's details, line items, or display settings
Permanently delete a credit note from FreeAgent
Create a new estimate, quote, or proposal in FreeAgent for a specified contact
Retrieve all estimates with optional filtering by contact, project, invoice, status, and date range
Retrieve a single estimate by ID with full line items, status, and VAT details
Update an existing estimate's details, notes, or display settings
Permanently delete an estimate from FreeAgent (cannot delete estimates with Invoiced status)
Add a new line item to an existing estimate
Update an existing estimate line item
Remove a line item from an estimate
Retrieve the default additional text shown on all estimates
Update the default additional text shown on all estimates
Remove the default additional text from all estimates
Create a new out-of-pocket expense or mileage claim in FreeAgent
Retrieve all out-of-pocket expenses with optional filtering by user, project, status, and date range
Retrieve a single expense by ID with full category, tax, rebill, and attachment details
Update an existing expense's details, tax, rebill settings, or recurring schedule
Permanently delete an expense from FreeAgent
Create a new draft invoice in FreeAgent with line items and optional auto-billing of timeslips, expenses, or estimates
Retrieve all invoices with optional filtering by contact, project, status, date range, and sort order
Retrieve a single invoice by ID with full line items, payment status, and payment methods
Update an existing invoice's details, line items, payment methods, or display settings
Permanently delete an invoice from FreeAgent
Retrieve the default additional text shown on all invoices
Update the default additional text shown on all invoices
Remove the default additional text from all invoices
Create a new project in FreeAgent linked to a contact with budget, billing rate, and IR35 settings
Retrieve all projects with optional filtering by contact, status, sort order, and nested contact details
Retrieve a single project by ID with full budget, billing, and IR35 details
Update an existing project's name, status, budget, billing rate, or other settings
Permanently delete a project from FreeAgent
Retrieve all recurring invoice profiles with optional filtering by contact, project, and status
Retrieve a single recurring invoice by ID with full schedule, line items, and payment methods
Create a new task under a specific project in FreeAgent
Retrieve all tasks with optional filtering by project, status, date, and sort order
Retrieve a single task by ID with full billing rate, status, and deletability info
Update an existing task's name, billing rate, status, or billable flag
Permanently delete a task from FreeAgent
Create a new timeslip (time entry) in FreeAgent for a user, task, and project
Retrieve all timeslips (time entries) with optional filtering by user, project, task, status, and date range
Retrieve a single timeslip by ID with full hours, billing, and timer details
Update an existing timeslip's hours, date, task, project, user, or comment
Permanently delete a timeslip from FreeAgent
Create a new user with a specified role and permission level in FreeAgent
Retrieve all users with optional filtering by role type (staff, advisors, active)
Retrieve a single user by ID with full role, permissions, and tax details
Update an existing user's details, role, or permissions
Permanently delete a user from FreeAgent
Retrieve the authenticated user's personal profile (minimum Time access)
Update the authenticated user's own profile (minimum Time access)
Upload bank transactions as a JSON array to a specific bank account
Retrieve all accounting categories grouped by type (admin expenses, cost of sales, income, general)
Retrieve the authenticated company's profile, settings, and tax configuration
Retrieve all available business category values for the company profile
Retrieve upcoming tax events and deadlines for the company
Download a credit note as a base64-encoded PDF
Download an estimate as a base64-encoded PDF
Retrieve mileage rates and engine type/size options for expense claims
Download an invoice as a base64-encoded PDF
Retrieve a timeline of invoice payment events and activities
Send a credit note via email (credit note must be in Open status, not Draft)
Transition a credit note from Draft to Open status, or re-open a cancelled credit note
Transition a credit note back to Draft status
Create a copy of an existing estimate with Draft status and today's date
Send an estimate via email with optional attachments or using an email template
Transition an estimate to Sent status
Transition an estimate back to Draft status
Transition an estimate to Approved status
Transition an estimate to Rejected status
Convert an estimate to an invoice, setting estimate status to Invoiced
Create a copy of an existing invoice with Draft status and today's date
Send an invoice via email with optional attachments, expense receipts, or using a template
Transition an invoice from Draft to Open status, or re-open a cancelled invoice
Transition an invoice to Scheduled To Email status
Transition an invoice back to Draft status
Write off an invoice as unpaid (must be sent with due date in the past)
Convert a draft negative invoice to a credit note
Take payment for an invoice using a GoCardless Direct Debit Mandate
Start a running timer on a timeslip to track time in real-time
Stop a running timer on a timeslip and record the elapsed time
Connect your AI agent to FreeAgent and help your team scale the finance operations they run by hand today.
Automate invoice processing with AI agents connected to your ERP, accounting software, and AP tools through StackOne.
ViewUse StackOne to connect your AI agent to your accounting, CRM, and messaging systems to automate Accounts Receivable dunning and payment follow-up.
ViewUse StackOne to connect your AI agent to your accounting, email, and document management systems to automate invoice processing and purchase order matching.
ViewOne endpoint. Any framework. Your agent is talking to FreeAgent in under 10 lines of code.
MCP Clients
Agent Frameworks
{
"mcpServers": {
"stackone": {
"command": "npx",
"args": [
"-y",
"mcp-remote@latest",
"https://api.stackone.com/mcp?x-account-id=<account_id>",
"--header",
"Authorization: Basic <YOUR_BASE64_TOKEN>"
]
}
}
}138+ actions
125+ actions
107+ actions
95+ actions
82+ actions
70+ actions
70+ actions
Anthropic's code_execution processes data already in context. Custom MCP code mode keeps raw tool responses in a sandbox. 14K tokens vs 500.
11 min
Benchmarking BM25, TF-IDF, and hybrid search for MCP tool discovery across 916 tools. The 80/20 TF-IDF/BM25 hybrid hits 21% Top-1 accuracy in under 1ms.
10 min
MCP tools that read emails, CRM records, and tickets are indirect prompt injection vectors. Here's how we built a two-tier defense that scans tool results in ~11ms.
12 min
origin_owner_id.All the tools you need to build and scale AI agent integrations, with best-in-class connectivity, execution, and security.