How to use Claude with the BOE in an accounting firm: free connector, installation and 5 real queries

Update of 3 October. The Spanish Congress repealed Real Decreto-ley 27/2026 on 2 October, the same day it came into force (BOE-A-2026-20527). What follows is what the connector returned on the 1st; it works as an example of how it operates, not as the current state of article 10 of the LAU (Spanish Urban Leases Act).

How this article was written. boe-mcp is our own project: we say so up front, so that you can take it into account as you read. The five queries below were run on 1 October 2026 with the connector's tools against the BOE's open data API, and what we show is what they returned. The data of Real Decreto-ley 27/2026 are also checked on its page on boe.es. The titles of Spanish legal provisions are given in Spanish, as published. This is information, not legal or tax advice.

Quick answer

boe-mcp is a free, open-source connector (MIT licence) that lets Claude query the BOE directly, without copying and pasting. It works with Claude Desktop and Claude Code, needs no BOE keys or accounts and only connects to boe.es.

Code and instructions: github.com/Proxera-Group/boe-mcp.

The problem: the BOE does not warn you

The BOE comes out from Monday to Saturday. The one of 1 October 2026 carries 201 entries: 6 general provisions, 51 on authorities and staff, 27 "other provisions" and 117 announcements. Of the 6 general provisions, three are grants, one regulates a waste register and another publishes the last-resort tariff for natural gas. The sixth is Real Decreto-ley 27/2026, which changes the extension of leases of a main home and comes into force the next day.

Watching it by hand means opening the summary every morning, reading titles and deciding what affects which client. The connector does not decide for you. What it does is let Claude read the BOE for you and bring you what matches what you watch, with the identifier and the link to check it.

Installation step by step

You need Python 3.11 or higher. The most convenient route is uv, which downloads and runs the connector without installing anything by hand. It is installed straight from GitHub.

In Claude Code

A single command:

claude mcp add boe -- uvx --from git+https://github.com/Proxera-Group/boe-mcp boe-mcp

To see that it has been registered: claude mcp list.

In Claude Desktop

1. Go to Settings → Developer → Edit config, which takes you to the claude_desktop_config.json file.
2. Add this:

{
  "mcpServers": {
    "boe": {
      "command": "uvx",
      "args": ["--from", "git+https://github.com/Proxera-Group/boe-mcp", "boe-mcp"]
    }
  }
}

3. Restart Claude Desktop.

If you prefer pip to uv:

pip install git+https://github.com/Proxera-Group/boe-mcp

and in the configuration put "command": "boe-mcp", with no args.

Disk cache (optional)

export BOE_MCP_CACHE_DIR=~/.cache/boe-mcp

In Claude Desktop it is added inside the "boe" block as "env": { "BOE_MCP_CACHE_DIR": "/path/to/the/cache" }. It keeps past summaries, rules and searches for a short time; the day's summary, 10 minutes. Without the variable nothing is saved.

Five real queries, with what they returned

All run on 1 October 2026. If you repeat them on another day, the results change: it is the BOE of that day.

1. "What has come out on housing and rentals in the last three days?"

novedades(["vivienda"], 3) reviewed the summaries from 29 September to 1 October and found 2 matches:

Each result comes with its HTML and PDF link on boe.es.

2. "What does Real Decreto-ley 27/2026 amend?"

leer_documento("BOE-A-2026-20385") returns the text and these data:

• Published: BOE no. 243, of 1 October 2026. Section I, Head of State.
• References: AMENDS art. 10 of Ley 29/1994, on Urban Leases (BOE-A-1994-26003) · IN RELATION TO final provision 5 of Real Decreto-ley 26/2026 (BOE-A-2026-20266) · CITES Real Decreto-ley 7/2019.
• Subjects: urban leases, consumers and users, contracts, compensation, housing.

Its second final provision says it comes into force «el día siguiente al de su publicación», that is, the day after its publication: 2 October 2026, the date shown in the analysis on boe.es.

3. "What is the current wording of article 10 of the LAU, and is any change about to come into force?"

leer_norma("BOE-A-1994-26003", bloque="a10"). The BOE had already incorporated the change into the consolidated text on that same 1 October, and the tool returns two versions of the article with a warning: «Hay texto publicado que aún no está en vigor», that is, there is published text that is not yet in force.

The second column is what the connector returned on 1 October, not the current law: Real Decreto-ley 27/2026 was repealed on 2 October (see the update above). The royal decree-law also had a transitional regime for existing contracts. For example: if less than six months remain before expiry when it comes into force, the landlord may still give four months' notice. Before applying it to a client, read it in full in its single transitional provision.

If this is your case: Xera for accountancy firms (ES) →

This is the case where the connector pays off most: seeing in a single answer what the law says today and what it will say tomorrow.

4. "Give me the tax news of the last week"

novedades(["fiscal"], 7), from 25 September to 1 October: 7 matches. Among them, the effective interest rate for the fourth quarter of 2026 for the tax qualification of financial assets (BOE-A-2026-20144) and two addenda to agreements of the Tax Agency.

Two Guardia Civil decorations also come up (BOE-A-2026-19917 and BOE-A-2026-19924), because their titles contain the word "Fiscal" as a person's post. It is a false positive, and it helps to understand how novedades works: it filters by keywords in the title; it does not understand the content.

The same query with the employment profile and 14 days (from 18 September to 1 October) gave 23 matches, with several collective agreements registered by the Dirección General de Trabajo.

5. "Which data-protection rules are still in force?"

buscar_legislacion("protección de datos", solo_vigentes=true) returns 10 rules. The first is Ley Orgánica 3/2018 (LOPDGDD), and the Statute of the AEPD and the laws of the Catalan and Basque data-protection authorities also appear.

Two warnings that can be seen in the result itself:

• Ley Orgánica 15/1999 appears as "in force". When its record is requested with leer_norma, the BOE states: «SE DEROGA con las excepciones indicadas, por Ley Orgánica 3/2018». A rule repealed only in part appears as in force: you have to read its references.
• A Civil Protection resolution slips in about telephone numbers for dangerous-goods accidents, because its title contains "protección", "de" and "datos". The search is by words.

How to ask so that it is useful

• Always ask for the BOE identifier and the link (for example, BOE-A-2026-20385). That way you check the source in seconds.
• For what was published today, the daily summary. Consolidated legislation may lag behind the day's BOE; for a provision that has just come out, have it use leer_documento.
• Long rules, by articles. The VAT Act has 307 blocks in its consolidated text: Claude reads the index and then only the articles you need.

Limits, plainly

• It is not legal or tax advice. It is a query tool. The official text prevails on boe.es: check it before acting or advising a client.
• Claude may summarise or interpret a legal text wrongly. What matters is checked against the original.
• The news works by keywords in the title. It serves for watching, not for guaranteeing that nothing is missed. You have seen a false positive above; there may also be omissions.
• It covers only what the BOE's API provides: the BOE and the consolidated legislation it maintains, including part of the regional legislation published in it. It does not include the Official Journal of the EU, the regional gazettes themselves (DOGC, BOJA and others), case law or administrative doctrine such as the DGT's binding rulings.
• "In force" is what the BOE declares. Rules repealed only in part appear as in force.
• A consolidated text may carry changes that are not yet in force. The connector returns the version in force today and warns of the next one, as in the LAU example, but the dates should be checked.
• By default it leaves out announcements (section V) and staff (section II), because of volume.
• About your data: the connector only connects to boe.es. The conversation with Claude is processed by Anthropic, as with any use of Claude.

Frequently asked questions

How much does it cost? The connector is free and open source, with an MIT licence. Claude is used with your Anthropic account, on its terms.

Is a BOE key needed? No. The BOE's open data API is public.

Is it an official BOE service? No. It uses the BOE's open data API, but it is not affiliated with the Agencia Estatal Boletín Oficial del Estado.

Does it warn you every morning on its own? Not by itself: it answers when asked. For the watch to be daily, someone or something has to ask it every day.

If you want this to work on its own

boe-mcp answers when you ask. In an accounting firm, the real work is in what comes next: knowing which clients a change affects, warning them and making sure a deadline is not missed.

That is what we do with XERA for accounting firms: an AI agent that runs on Claude, with the subscription in the firm's name, and that classifies invoices and documents, chases missing documentation, prepares drafts of quarterly tax filings and warns of deadlines. Plans and prices are at proxera.es/precios.

And if you only want the connector, it is yours: github.com/Proxera-Group/boe-mcp.

Sources

• Real Decreto-ley 27/2026, of 29 September, BOE no. 243, of 1 October 2026: BOE-A-2026-20385 (consulted on 1 Oct 2026).
• Ley 29/1994, on Urban Leases, consolidated text: BOE-A-1994-26003 (consulted on 1 Oct 2026).
• Ley Orgánica 15/1999, consolidated text: BOE-A-1999-23750 (consulted on 1 Oct 2026).
• BOE summaries from 18 Sep to 1 Oct 2026 and search in consolidated legislation, via the BOE open data API with boe-mcp, on 1 Oct 2026.
• boe-mcp, code and instructions: github.com/Proxera-Group/boe-mcp.

Published on 1 October 2026 by Robert Graf and Miller Espinosa, from Proxera. The results of the queries are those of that day; the BOE changes every morning.