Connect an AI assistant

What an assistant gives you

• It tells you what is due and by when, estimates the modelo 303 and the modelo 130 and works out the other returns from your books, by the rules of the Agencia Tributaria.
• It records incomes and expenses, from what you tell it or from a document you uploaded or mailed, and posts them, so that they count in your books as if you had done it.
• It confirms the movements of the bank statements you imported and matches them with the entries they pay.
• It prepares invoice drafts, templates and series and keeps your invoicing settings, short of issuing an invoice.
• It keeps the tax profile and prepares the returns and the Renta as drafts you review, short of filing them.

A receipt or an invoice, as a PDF or a photo, can reach your business by mail, at the address the business holds for documents. The assistant can tell you that address or, with your consent, forward a mail of yours to it. A photo may be a JPEG, PNG, HEIC, HEIF or WebP file. What arrives becomes a document that you confirm.

A bank statement, the datos fiscales and the papers of the first run you upload yourself in the Trimestria application; the assistant cannot take them from the conversation. It then works with what you uploaded.

What you can ask

A few examples:

• What do I have to file this quarter, and by when?
• I paid 68.40 euros for fuel today - add it to my books as an expense and post it.
• Match yesterday's bank movement of 1,210 euros with the invoice it pays.
• Prepare an invoice draft for my client for 10 hours of consulting at 50 euros.
• Prepare my 303 for the third quarter and tell me what is left to review.

Connect Claude

You need a Claude plan that lets you add a custom connector. Anthropic decides which; the help of Claude explains it.

1. In Claude, open the connectors (Customize > Connectors) and choose to add a custom connector.
2. Name it Trimestria, enter the address https://mcp.trimestria.es/mcp and add it.
3. Choose Connect. Trimestria's consent page opens in your browser. Sign in if you are asked to.
4. Choose what the assistant may do, as described under "What you choose when you allow access", and allow access.
5. Back in Claude, ask something, for example: "What do I have to file this quarter, and by when?"

Add Trimestria in Claude

Connect ChatGPT

Where ChatGPT lets you add a custom connector by its address, it works the same way. OpenAI decides which plans can; its help page on custom MCP connectors says where to start.

1. In ChatGPT, open the settings where connectors are added and choose to create a custom one.
2. Name it Trimestria, enter the address https://mcp.trimestria.es/mcp and choose OAuth as the way to sign in.
3. Connect. Trimestria's consent page opens: sign in, choose what the assistant may do and allow access.
4. Ask something in a new conversation, with Trimestria turned on for it.

What you choose when you allow access

The consent page is in the Trimestria application. On it you choose:

• Who allows it: only the owner of the business can allow access to it.
• The business: an assistant works in one business only. To use another one, connect again.
• The product you connect from: Claude, ChatGPT or Codex, on any of their plans, personal or of an organisation. No access is granted from another product.
• The permissions, seven in all: reading deadlines, open tasks and the quarter estimate is always included. Tick the others you want: reading documents, entries, contacts and invoices; documents; entries and contacts; the bank; the invoicing, without issuing; the taxes, without filing.
• How long: up to 365 days, 90 by default. The assistant renews its short-lived keys by itself until the access ends, or until 90 days pass without use.
• The terms: you accept the terms of assistant access, section 7 of the Terms of service, and allow access in your signed-in session. No code is asked at this step.

A personal token for command-line agents

Agents that run on your computer, such as Claude Code or Codex, can also connect with a personal token instead of the consent page.

Assistant access depends on the plan of the business. The Connected agents page tells you when yours does not include it.

1. In Trimestria, open Settings > Connected agents and choose Create a personal token.
2. Give it a name you will recognise, choose the permissions and the lifetime, from 1 to 365 days and 90 by default, and confirm with your second factor.
3. Copy the token now. It is shown only once.
4. Give it to the agent as a bearer token for https://mcp.trimestria.es/mcp. In Claude Code, for example:

claude mcp add --transport http trimestria https://mcp.trimestria.es/mcp --header "Authorization: Bearer <your-token>"

The tools an assistant can use

The server offers the tools below.

Every tool works in the business you connected and within the permissions you allowed.

• what_is_dueWhat is dueReads only

  Shows which returns are open and not yet filed, with their deadlines, and the calendar of the year with the reason each obligation arose. It files and pays nothing.

• quarter_estimateQuarter estimateReads only

  Estimates the modelo 303 and the modelo 130 of a quarter, box by box, from your posted entries. It is an estimate: nothing is saved, filed or paid.

• read_the_catalogueRead the catalogueReads only

  Reads the lists Trimestria works with: the categories of income and expense, the kinds of activity, the IAE headings, the VAT rates in force, the types of street and the towns of a postal code.

• find_the_postal_codeFind a postal codeReads only

  Asks the public CartoCiudad service for the postal code of a Spanish street and number, as the address forms of the application do. It saves nothing.

• describe_actionsDescribe the actions of a toolReads only

  Tells the assistant what each action of a tool asks for and what it answers, so it can call it correctly. It reads nothing of your business.

• searchSearch the businessReads only

  Searches your contacts, issued invoices, documents and book entries by text.

• read_documentsRead the documentsReads only

  Shows a document with its state, what rests on it and what Trimestria read in it, the expense decided for it, how it would post, and your mail address for documents.

• read_filesRead a fileReads only

  Hands the assistant a file the application serves: the original of a document, an invoice PDF or preview, the books of a year, a filing receipt or a withholding certificate.

• read_onboardingRead the first runReads only

  Shows the papers, the facts read and the contacts offered in the first run of the business.

• read_entriesRead the book entriesReads only

  Shows an income or an expense with its history, the entries that look like it, its withholding, the bank movements that may pay it and what removing it would change.

• read_booksRead the booksReads only

  Shows what the books hold beyond one entry: the totals of a quarter, the periods declared empty, the recurring expenses, the properties and the papers kept for a contact.

• preview_booksPreview imported booksReads only

  Reads supported invoice books and Diario reports supplied for this preview, shows source discrepancies and possible matches, and keeps tax treatments for confirmation. It stores no files and posts no entries.

• import_booksImport booksAdds data

  Keeps a resumable book import, freezes your manual decisions and applies confirmed groups. Upload remains available when reading entitlement is closed. It files and pays nothing.

• propose_entry_valuesPropose the values of an entryReads only

  Proposes the category, the share, the withholding or the EU sales threshold for an entry, as the application proposes them. It only proposes: nothing is saved.

• read_counterpartiesRead the contactsReads only

  Searches and shows your clients and suppliers, with their VIES and census checks and the unit last invoiced.

• read_bankingRead the bankReads only

  Shows your bank statements and their movements, what each movement may settle, what it already settles and how it would post.

• read_invoicesRead the invoicesReads only

  Shows your invoices, drafts, test invoices, series and templates.

• read_invoicing_settingsRead the invoicing settingsReads only

  Shows what your invoices print: the details, the addresses of the business, the payment accounts and the designs.

• read_tax_profileRead the tax profileReads only

  Shows the tax profile of the business, the declarant, the census check, earlier figures, the filing options and what applies to you.

• calculate_returnsCalculate a returnReads only

  Works out the modelo 111, 115, 180, 190, 349 or 390 from your books, by the rules of the Agencia Tributaria. Nothing is saved or filed.

• read_returnsRead the returnsReads only

  Shows the returns Trimestria prepared, their checks and files, their validations and the filings you made, with their receipts.

• read_rentaRead the RentaReads only

  Shows the Renta of a year: the activity figures, the datos fiscales, the return prepared, its filing and the ways of paying.

• read_the_businessRead the businessReads only

  Shows the name and NIF of the business, what keeps it in place, its record of actions and the state of an export.

• upload_documentUpload a documentAdds data

  Adds a receipt or an invoice to your books, with the same checks as an upload in the web application. A file you already hold is not stored twice.

• write_documentsAdd a paper to the first runAdds data

  Hands the first run a paper, as you would drop one on its first step.

• change_documentsChange a documentChanges or removes data

  Gives a document its kind, confirms what was read in it, decides its expense, reads it again or withdraws it, and chooses the model it is read with.

• record_entryRecord an income or an expenseAdds data

  Records an income or an expense in your books, unposted until you or the assistant post it.

• write_booksAdd to the booksAdds data

  Records a property, keeps a paper for a contact, states a payment or marks an expense as recurring.

• change_entriesChange a book entryChanges or removes data

  Amends an entry, attaches the invoice it awaited or corrects a property. A posted entry changed counts at once, its earlier version kept.

• post_entriesPost the book entriesChanges or removes data

  Posts entries, a reverse charge or a paper with its movement, with the same checks as in the application. What is posted counts in your books.

• remove_entriesAnnul or delete an entryChanges or removes data

  Annuls a posted entry or deletes an unposted one, cancels a stated payment or ends a recurring expense.

• write_counterpartiesAdd a contactAdds data

  Creates a client or a supplier, or confirms the contacts the first run offered.

• change_counterpartiesChange a contactChanges or removes data

  Amends a contact and asks VIES to check its number again. An invoice already issued keeps what it printed.

• write_bankingBring to the bankAdds data

  Imports a bank statement in any format, or brings a document for a movement and records its expense.

• change_bankingChange the bankChanges or removes data

  Accepts a statement, confirms and sorts its lines, records or cancels a match and posts a movement.

• write_invoicingAdd to the invoicingAdds data

  Creates invoice drafts, corrections, series, templates, addresses and designs. A draft is not issued: it takes no number and nothing is sent.

• change_invoicesChange an invoiceChanges or removes data

  Amends a draft, marks an invoice paid or removes that payment, deletes a draft and renames or removes a template.

• change_invoicing_settingsChange the invoicing settingsChanges or removes data

  Changes the details, addresses, signature and designs your invoices print, and removes a payment account. It never adds or changes one.

• prepare_returnsPrepare a returnAdds data

  Prepares a return or the Renta from your books, checks it and asks for its file: a draft you review and file yourself in the application.

• change_tax_profileChange the tax profileChanges or removes data

  Records what you state about the activity, the declarant, earlier figures and the name of the business.

• change_returnsChange a returnChanges or removes data

  Records whether a filed return was paid, stops a send waiting in its window, and takes the facts and the datos fiscales of the Renta. It files and pays nothing.

• ask_the_agencyAsk the Agencia TributariaChanges or removes data

  Queues a question to the Agencia: the census, the validation of a file, the datos fiscales or the ratifications of the Renta. Nothing is filed.

What an assistant can never do

Whatever permissions you allow, an assistant cannot do the following. It stays with you, in the Trimestria application.

• File, confirm or pay a return, or choose how it is filed or paid.
• Ask for or read an artificial intelligence model’s review of a prepared return.
• Issue an invoice.
• Add, change or make default a payment account, correct the NIF of the business, or delete it.
• Turn reading with artificial intelligence on or off, or download the complete archive of the business.
• Change your sign-in, your second factor, your security settings or who else has access.
• Do anything that needs your second factor or that cannot be undone.

Do not give an assistant your password, your second-factor codes or your recovery means.

What the assistant is shown, and what stays with you

What an assistant prepares is an estimate or a draft for you to check. It is not tax advice, and the responsibility for what you file stays with you.

• Other people's tax identification numbers are masked in every answer.
• Records of special categories of personal data, such as health, are left out of every answer. Only how many were left out is told.
• Text inside your documents reaches the assistant as untrusted content to report on, never as instructions to follow.
• The provider of the assistant receives what the assistant reads, and may process it outside the European Economic Area. Read its policies before you connect.

Limits

Every access has its own limits: 60 calls a minute, 2000 calls a day and 200 writes a day. When a limit is reached the assistant is told, and can try again later.

On the Subscription a business has up to 1000 assistant actions a month, counted over all its accesses; the Pro plan has no monthly allowance. An action is one request of the assistant to Trimestria; a usual question takes 5 to 15, and errors and refusals are not counted. The Connected agents page shows how many are used this month.

Trimestria may suspend a connection for abuse, a breach of the terms or a security risk, and will say why unless the law or security prevents it.

Revoke access

Open Settings, then Connected agents, and choose Revoke access on the access you want to end. The assistant loses access on its next call. A call already in progress is allowed to finish.

Revoking does not delete the copies the provider of the assistant has already received. An access also ends when it reaches the date you chose, when your account is being closed or when you leave the business. If the business no longer has a plan that includes assistant access, its use is suspended.

More

The terms of assistant access are section 7 of the Terms of service. What is processed, and for how long, is in the Privacy policy. For a question or a problem, write to support.

• Terms of service, section 7
• Privacy policy
• Support