Connector guide

Use comma from Claude and ChatGPT

Last updated October 2, 2026

Connect your books to an AI assistant, see exactly what it can do, and know what it asks before it acts. IT admins: start with security; if something is not working, see troubleshooting.

Overview

comma runs a remote Model Context Protocol (MCP) server. Add it to Claude (web, desktop and mobile), Claude Code, or ChatGPT in developer mode, and the assistant can read your reports and do bookkeeping work in your companies by calling comma's tools directly.

https://trycomma.app/api/mcp

The connector covers company accounting: your ledger, sales, purchases, banking, GST/HST and period end. It can never do more than your role in a company allows, and it never moves money.

What you need

A company on the Pro or Premium plan, including the 30-day trial (card required). On the Basic plan the connector refuses every call, reads included, and the books stay fully available in the browser.
Membership in that company. The assistant works only in companies you belong to.
Your role in each company decides what the assistant can do there:

What each comma role allows through the connector
Role	What the assistant can do for you
Admin	Everything an accountant can, plus editing the company profile (legal name, business number and other tax-profile details). Inviting people and billing stay in the browser.
Accountant	All accounting: post and reverse journals, record and void payments, pay and void bills, reconcile, prepare GST/HST returns and record remittances, close and reopen years.
Member	Read the books, create and send invoices, enter bills and vendors, and categorize and book bank transactions. Cannot post manual journals, record payments, void anything, or reconcile.
Viewer	Read only: reports, ledgers, documents and the audit log.

Connecting

Claude (web, desktop and mobile)

Open Customize › Connectors. Add comma from the connector directory, or choose + › Add custom connector and paste the server URL.
On a Team or Enterprise plan, an Owner adds the connector first under Organization settings › Connectors; members then choose Connect.
Sign in to comma and choose Authorize. Once added, the connector also works in the Claude mobile apps.

Claude Code

Run the command below in a terminal.
Start Claude Code, run /mcp, choose comma, and complete sign-in in the browser window that opens.

claude mcp add --transport http comma https://trycomma.app/api/mcp

ChatGPT (developer mode)

Turn on developer mode under Settings › Security and login.
Open chatgpt.com/plugins, choose +, paste the server URL, and complete sign-in.

What the assistant can do

Reads never change anything. Writes go through the same validated services as the web app. Tools marked Claude asks first post, void, send or record a payment, so Claude asks you to approve each call. Tools marked Emails customer send an email to your customer. The tables list the main tools; the assistant sees the full set.

Reports and answers

Every figure is derived from the posted ledger at the moment you ask, never from a cached balance.

Reports and answers tools
Tool	What it does
`comma_report`Read	Profit and loss, balance sheet, cash flow and trial balance for any period.
`comma_dashboard`Read	Cash, income, outstanding balances, runway and recent activity.
`comma_ledger_lines`Read	General ledger detail for an account and period.
`comma_receivables_aging`Read	Who owes you, and how overdue each balance is.
`comma_payables_aging`Read	What you owe vendors, by age.
`comma_year_end_review`Read	What still stands between a fiscal year and its close.
`comma_audit_log`Read	Who changed what and when, including the assistant's own actions.

Sales

Drafts book nothing. Sending an invoice posts it and emails it to your customer.

Sales tools
Tool	What it does
`comma_customers_list`Read	Customers and their contact details.
`comma_invoices_list`Read	Invoices by status, customer or date, or one invoice in full.
`comma_payments_list`Read	Customer payments received.
`comma_customer_create`Write	Add a customer.
`comma_invoice_create`Write	Create a draft invoice.
`comma_invoice_send`WriteClaude asks firstEmails customer	Issue an invoice, post it, and email it.
`comma_invoice_remind`WriteEmails customer	Email a payment reminder for unpaid invoices.
`comma_customer_statement_send`WriteEmails customer	Email a customer statement.
`comma_payment_record`WriteClaude asks first	Record a payment you received against invoices.
`comma_credit_note_issue`WriteClaude asks firstEmails customer	Issue a credit note, post it, and email it.
`comma_invoice_void`WriteClaude asks first	Void an invoice and reverse its entries.

Purchases

Entering a bill posts it to accounts payable; paying it records a payment you made elsewhere.

Purchases tools
Tool	What it does
`comma_vendors_list`Read	Vendors and their details.
`comma_bills_list`Read	Bills by status, vendor or date, or one bill in full.
`comma_vendor_create`Write	Add a vendor.
`comma_bill_create`WriteClaude asks first	Enter a bill and post it.
`comma_bill_pay`WriteClaude asks first	Record a payment made on a bill.
`comma_bill_void`WriteClaude asks first	Void a bill and reverse its entries.

Banking and reconciliation

Bank rows arrive unreviewed. Reviewing a row is what books it.

Banking and reconciliation tools
Tool	What it does
`comma_bank_accounts_list`Read	Bank and card accounts.
`comma_transactions_list`Read	Bank transactions, filtered by review state, account or date.
`comma_match_candidates`Read	Open invoices or bills a transaction could settle.
`comma_reconciliations_list`Read	Reconciliation sessions and their status.
`comma_transactions_import`Write	Import transactions parsed from a bank statement; they arrive unreviewed.
`comma_transaction_categorize`WriteClaude asks first	Set the category on unreviewed transactions, ready for review.
`comma_transactions_review`WriteClaude asks first	Review a bank transaction, which books it.
`comma_transaction_match`WriteClaude asks first	Settle an invoice or bill with a bank transaction.
`comma_transaction_transfer`WriteClaude asks first	Book a transfer between two of your accounts.
`comma_reconciliation_start`Write	Start reconciling an account against a statement.
`comma_reconciliation_finish`WriteClaude asks first	Finish a reconciliation.
`comma_reconciliation_undo`WriteClaude asks first	Void a completed reconciliation.

Journals and the chart of accounts

Every entry must balance before it posts. A posted entry is corrected by a reversal, never edited.

Journals and the chart of accounts tools
Tool	What it does
`comma_accounts_list`Read	The chart of accounts.
`comma_journal_entries_list`Read	Journal entries, or one entry with its lines.
`comma_journal_entry_validate`Read	Check a proposed entry without saving it.
`comma_account_create`Write	Add a ledger account.
`comma_journal_entry_draft_create`Write	Save a draft journal entry.
`comma_journal_entry_post`WriteClaude asks first	Post a manual journal entry.
`comma_journal_entry_void`WriteClaude asks first	Reverse a posted entry, or void a draft.

GST/HST and period end

Returns are prepared from the tax recorded on your documents. comma records remittances; it never sends them.

GST/HST and period end tools
Tool	What it does
`comma_sales_tax_return_list`Read	GST/HST returns and their status.
`comma_book_lock_get`Read	The date your books are locked through.
`comma_depreciation_preview`Read	What the next book depreciation run would post.
`comma_year_close_list`Read	Each fiscal year's close and reopen history.
`comma_sales_tax_return_create`Write	Start a GST/HST return for a period.
`comma_sales_tax_return_prepare`WriteClaude asks first	Freeze a return's figures for review.
`comma_sales_tax_return_record_remittance`WriteClaude asks first	Record the GST/HST you paid and post it.
`comma_depreciation_run_post`WriteClaude asks first	Post a book depreciation run.
`comma_book_lock_update`WriteClaude asks first	Lock or reopen accounting periods.
`comma_year_close_close`WriteClaude asks first	Close a fiscal year into retained earnings.
`comma_year_close_reopen`WriteClaude asks first	Reopen a closed fiscal year.

What stays in the browser

Some actions stay in the comma web app on purpose. The assistant can tell you where to go: it lists them with comma_secure_actions_list.

Signing in, two-factor authentication, and deleting your account. Credentials and one-time codes never pass through a connector.
Creating or deleting a company. Creating one can start a paid subscription; deleting one is irreversible.
Inviting people, changing roles, and removing members. These decide who can see the books.
Billing and your subscription. Financial commitments are confirmed by the billing owner.
Document branding. A logo and accent colour need a person looking at the result.
Reviewing and revoking connections, and approving a new one. These change the security boundary itself (Settings › Connections).
Linking a bank through Plaid, and connecting a Gmail or Outlook mailbox. Each is a sign-in with the provider; its credentials never reach a connector.
Permanently deleting an account's history. An irreversible purge under an admin's typed confirmation. A connector can preview and archive instead.
Settings other than the company profile. Sales-tax registrations, report layouts, roles, security and audit settings are readable but not changeable through a connector.

Settings are read-only through the connector, apart from the company profile, which an admin can update with comma_company_update.

Safety

Approval before it posts. Tools that post, void, send or record a payment are flagged as destructive, so Claude asks you to approve each call. If you set a tool to always allow, that prompt goes away — choose that only for tools you are comfortable running unattended.
Your name, marked as AI. Every action is written to the company's audit log under the name of the person who connected the assistant, with an AI marker beside it.
No double booking. Write tools that create records take an idempotency key, so a retried request returns the first result instead of booking twice. Where a tool carries the version the assistant read, a record someone changed in the meantime is refused rather than overwritten.
Closed periods stay closed. A posting dated in a locked period or a closed year is refused, exactly as it is in the browser.
Corrections are reversals. A posted entry is never edited or deleted. Voiding it posts an exact reversing entry, and both stay in the ledger.
It never moves money. comma records payments that happened elsewhere. No tool can send, pull or transfer funds.

Security for IT admins

How the comma connector authenticates and protects access
Authorization	OAuth 2.1 authorization code flow with PKCE (S256). Clients register dynamically or identify themselves with a client ID metadata document.
Access tokens	15 minutes when the token can change the books (as a full connection can), otherwise one hour.
Refresh tokens	30 days, rotated on every use. A retry within 60 seconds receives the same new pair, so a dropped response does not disconnect you; reuse after that revokes the connection.
Authorization codes	10 minutes, single use.
Token storage	Tokens are opaque and stored only as keyed hashes, bound to the comma MCP endpoint and to one connection grant.
Revocation	Revoking a connection deletes its access tokens and revokes its refresh tokens; the assistant's next request is refused with 401.
Per-call checks	Every call re-checks the connection, your live membership, the company's plan and your current role, so a change applies to the very next call.
Conversation data	comma receives only the inputs of each tool call — never your chat history, the assistant's memory, or files you did not ask it to send.
Telemetry	Tool name, duration, error category, and user and company identifiers. Never the inputs or the results.

Discovery documents follow RFC 9728 and RFC 8414: the protected resource metadata is at /.well-known/oauth-protected-resource/api/mcp and the authorization server metadata at /.well-known/oauth-authorization-server/api/auth. The service providers that process data for comma are listed in the privacy policy.

Admin controls

Each person reviews and revokes their own connections at Settings › Connections. Revoking takes effect on the assistant's next request.
An admin who removes a member or changes a role changes what that person's assistant can do on its very next call. No token outlives the membership it was issued under.
A company outside an active plan becomes read-only: connector writes are refused with a message that nothing was changed, and its books stay readable and exportable.
Every assistant action is in the company's audit log, under the person's name, marked as AI.

Limits

Connector request and response limits
Limit	Value	When it is exceeded
Requests	About 120 per minute per connection	HTTP 429 with a Retry-After header saying how many seconds to wait before retrying.
Request size	1 MiB	HTTP 413. Upload larger receipts in the browser.
Result size	64 KiB per tool result	An error asking for a narrower filter or a smaller page. No partial financial data is returned.
Lists	Paginated	List tools return a page at a time; ask for the next page or narrow the date range.

Example prompts

“What was our net income last quarter, and which expense lines grew the most?” Uses comma_report.
“Which customers are more than 30 days overdue, and by how much?” Uses comma_receivables_aging.
“Categorize this month's unreviewed bank transactions, tell me which ones you weren't sure about, then book the rest.” Uses comma_transactions_list, comma_transaction_categorize, comma_transactions_review.
“Create an invoice to Northwind Co. for $2,400.00 of brand strategy, due in 30 days, and send it.” Uses comma_customers_list, comma_invoice_create, comma_invoice_send.
“Northwind paid their last invoice in full today by e-transfer. Record it.” Uses comma_invoices_list, comma_payment_record.
“Is last fiscal year ready to close? What's still open?” Uses comma_year_end_review.

Troubleshooting

“This company's plan does not include using comma from Claude or ChatGPT.”: The connector is part of the Pro and Premium plans, including their trial. The billing owner can change plans at Account › Billing. The books stay fully available in the browser.
“… is retained in read-only mode, so connectors cannot change it.”: The company is outside an active plan. Reads and exports still work; nothing was half-written. Changes resume once the billing owner restores the plan.
“Your current role lacks the … permission.”: Your role in that company does not allow the action. Ask an admin or accountant to do it, or to change your role. The change applies on the next call, with no reconnect.
“This connector can access more than one company.”: Tell the assistant which company you mean. It lists your companies and passes the one you name on each call.
“Couldn't reach the MCP server”, or the connection stops working: Remove the connector and add it again. Check that the URL is exactly https://trycomma.app/api/mcp, with no www and no trailing slash. If you revoked the connection in Settings › Connections, you must reconnect.
Claude Code says a tool's output is too large: Ask for a narrower date range or a smaller page, or raise Claude Code's limit by starting it with the MAX_MCP_OUTPUT_TOKENS environment variable set higher, for example MAX_MCP_OUTPUT_TOKENS=50000.

Support

Email support@trycomma.app and a person will answer. If a tool returned an error, include its request id if the assistant showed one. Privacy questions go to privacy@trycomma.app; see also the privacy policy and support.

Last updated October 2, 2026.

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