eur-lex-mcp-server

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Overview

EU legislation, CJEU case law, and treaties over the EU Publications Office's CELLAR semantic repository and the EUR-Lex content API. Search documents and case law, fetch full text, resolve citations, traverse the amendment and citation graph, and browse the EuroVoc thesaurus from any MCP client. Runs as a stdio process, a local Streamable HTTP server, or the public hosted endpoint above.

Tools

Tool	Description
eurlex_search_documents	Search EU legislation, treaties, and preparatory acts by type, date, EuroVoc subject, author institution, and in-force status
eurlex_get_document	Fetch metadata and full text (HTML, Markdown, or Formex4 XML) for an act or case by CELEX, ELI, or work URI, with a section outline of either
eurlex_lookup_celex	Resolve a CELEX number, ELI URI, ECLI, or OJ citation (Regulation (EU) 2016/679) to its canonical CELLAR work
eurlex_get_cases	Search CJEU and General Court case law by case number, court, case type, and date range
eurlex_get_relations	Traverse the CELLAR relationship graph — amendments, repeals, consolidations, legal basis, citations, transpositions
eurlex_browse_subjects	Search the EuroVoc thesaurus to resolve terms to concept URIs
eurlex_query_sparql	Run a raw, read-only SPARQL SELECT against the CELLAR endpoint

Resources

Resource	Description
eurlex://document/{celexNumber}	Metadata snapshot for a CELLAR work
eurlex://document/{celexNumber}/relations	One-hop relationship summary for a CELLAR work

All resource data is also reachable via tools.

Prompts

Prompt	Description
eurlex_comparative_analysis	Frame a comparative EU/US legal analysis for a policy domain

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Capability reference

eurlex_search_documents _tool

• At least one filter: keyword (English titles, plus CELEX numbers when it holds a digit: a whole CELEX with its (01)–(20) siblings and R(01)–R(20) corrigenda by exact lookup, a partial one such as 2016R0679, R0679, J0131, or the OJ C 2024/01469 through the CELEX full-text index; one opening with letters no digit follows, such as R(01), or with a year, a slash, and a number under four characters, such as 2017/111, by a scan of every CELEX that can take tens of seconds; a bare year or a fragment opening mid-year or mid-number, such as 0679R, matches titles only; no body search), document_type (REG, DIR, DEC, TREATY, JUDG, OPIN_AG, PROP, REC, each its full CELLAR authority family), date_from/date_to, eurovoc_concept (from eurlex_browse_subjects), author_institution, or in_force (true/false; false covers repealed, expired, and not-yet-in-force acts)
• Pages of up to 100 via offset/limit, newest first with the CELEX breaking date ties, so a page is the same on every call; each row flags is_consolidated and is_corrigendum, and corrigenda join only under include_corrigenda, consolidated texts of a document_type only under include_consolidated
• No match returns an empty page with a notice naming the filters and how to broaden them; typed errors: no_filters, invalid_date_range, invalid_author_institution and invalid_keyword (no letters or digits)

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eurlex_get_document _tool

• Exactly one of celex_number, eli_uri, or work_uri, served as the work the CELEX resolves to (see eurlex_lookup_celex); a work_uri carrying several CELEX numbers (a national implementing measure) serves its lowest, with a notice giving the count; body as html (default), markdown, or xml (Formex4) in any of the 24 EUR-Lex languages, falling back to English; title is in the language served, or English when CELLAR has none in that language
• author_institution(s) name each author by the English label of its CELLAR authority code — an EU institution or body (European Union, Council of the European Union), a member state (Netherlands), an MEP (VAN MIERT), or a national court — the same labels eurlex_search_documents accepts as author_institution; case law lists its advocates_general apart
• Case law also carries its ecli (the one eurlex_lookup_celex reports) and its English CELLAR title, in every language, parsed as eurlex_get_cases parses it: title is the parties (the court/AG descriptor when there are none), with formation, referring_court, subject_matter, and case_reference alongside, or the raw #-joined title when the parse misses part of it
• content_mode "paged" (default), "full", or "metadata_only", every body capped at 100,000 characters per call with content_chars_total/has_more to page on; outline: true lists chapter/section/article/annex headings with offsets, the preamble's recitals as one Recitals 1–173 entry (include_recitals: true lists each), and select (e.g. { articles: "1,5,17" }) returns just those sections, each source character once, under the same cap with no offset/limit, with selected_sections giving each one's own offset/chars for a paged read. Headings are read in the language served and labelled in English in every format (Article 4, CHAPTER IV); a selector number may carry an English kind word or the served language's (Artikel 4, 4. cikk). Headings of text an amending act inserts into another act are not the act's own and are skipped
• For a judgment, order, or AG opinion, outline lists each top-level section heading as served (Legal context, Sur les dépens), numbered by position, and a judgment's or order's ruling as one operative_part entry; select: { headings: "2" } returns a headed section up to the next heading, and select: { operative_part: true } the ruling alone to the end: from "On those grounds, …" in a modern body, from the "Operative part" section in a legacy one. Headings come from the body's heading markup in each CELLAR html generation and in Formex, so html, Markdown, and xml get the same outline; a summary-only body and some AG opinions carry no heading markup and outline empty
• is_superseded says whether a newer consolidated version than the text served is in effect (false on the newest one, and on a consolidated version dated after it that does not apply yet), with current_consolidated_celex/consolidated_as_of naming that version; resolve: "current_consolidated" serves it, for a base act or any of its consolidated texts; when no consolidated version is in effect yet, a notice says a future-dated consolidated text does not apply yet, or that resolve served the base act
• in_force: false comes with its reason where CELLAR records one: repealed_by (CELEX of the explicitly repealing acts), end_of_validity (omitted when open-ended; a future date on an act not yet in force), or entry_into_force (the earliest date, when still ahead)
• A consolidated text keeps its own title, date, and type and reports its base act as base_act_celex, with that act's authors, in_force and its reason, legal basis, and EuroVoc subjects; typed errors: invalid_identifier_args, not_found, content_challenge (a WAF bot-challenge in place of text)

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eurlex_lookup_celex _tool

• A CELEX number, ELI URI, ECLI, or OJ citation naming its act type and year (Regulation (EU) 2016/679, Regulation (EC) No 1049/2001, Directive 95/46/EC, Council Framework Decision 2002/584/JHA), parsed to its CELEX under identifier_type: "auto": No before the numbers means number/year, a two-digit year is 19YY, and the act type sets the CELEX letter (an ECSC Decision is S, a Framework Decision F, a Joint Action or Common Position E); a citation without its act type (95/46/EC) or year (Regulation No 17) is not parsed
• identifier_type auto-detects the format or sets it, and ambiguous_identifier fires when auto-detection can't classify the input, its recovery listing the accepted forms
• Returns work URI, confirmed CELEX number, resource type, date, and the case's ECLI (recorded on any work holding the CELEX); found: false for a well-formed identifier that matches no work, with a notice naming the CELEX, ELI, or ECLI tried and pointing to eurlex_search_documents
• A CELEX held by several works resolves to the one owl:sameAs its http://publications.europa.eu/resource/celex/{CELEX} IRI, which EUR-Lex serves the text from, else the lowest work URI, and every CELEX-taking tool and resource resolves the same way; an ECLI shared by several records resolves to the primary record with the lowest CELEX

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eurlex_get_cases _tool

• Filters: case_number (one case per value — C-131/12, T-22/20, F-12/05, or a pre-1989 26/62 — reaching every judgment, order, and AG opinion filed under it), court (CJEU or GC, by CELEX court letter), case_type (judgment, order, ag_opinion), keyword (English titles, plus CELEX numbers: a whole CELEX with its (01)–(20) siblings and _INF/_RES/_SUM/_EXT records, a partial one such as 2013CJ0131 or J0131 through the CELEX full-text index, one opening with letters no digit follows by a scan of every CELEX), and date_from/date_to; primary records only unless include_derivative adds notices, abstracts, summaries, and corrigenda
• Pages of up to 100 via offset/limit, newest first with the CELEX breaking date ties, so a page is the same on every call; each case carries its ECLI where CELLAR records one, plus formation, advocate_general, display_title, parties, referring_court, subject_matter, and case_reference parsed from the CELLAR title; the raw title comes back only when those fields miss part of it (an unrecognized segment, an "(Extracts)" marker, or a title date that differs from the case date)
• No match returns an empty page with a notice naming the filters and how to broaden them; typed errors: invalid_case_number, invalid_date_range, invalid_keyword (no letters or digits)

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eurlex_get_relations _tool

• Exactly one of celex_number or work_uri; relation_types narrows to any of cites, amends, amended_by, repeals, repealed_by, implicitly_repeals, implicitly_repealed_by, legal_basis, consolidated_version, national_transposition (omit for all)
• One hop, paged per relation type and direction via offset/limit (max 100, default 100), newest first with the work URI breaking ties, so a page is the same on every call; undated works come last
• Each relation carries relation_type, direction (outgoing/incoming), related_work_uri, related_celex_number when known, related_date (the date the page is ordered by) and related_title (the English title, whole) when the work has them, and on national_transposition rows related_member_state (ISO 3166-1 alpha-3, GBR for the United Kingdom) — national measures rarely carry an English title, and no other language stands in; empty_relation_types separates "no edges of this type" from "paged out", a work with no edges of the requested types returns an empty page with a notice, and typed errors are invalid_identifier_args and not_found

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eurlex_browse_subjects _tool

• Matches preferred and alternative EuroVoc labels, so a common synonym resolves to its concept, in any EU official language (default English); offset/limit pagination (max 50)
• Returns concept URI, preferred label, code, broader (parent) label, and the alternative label that matched when one did; an empty page with a notice when nothing matches
• Exact label matches rank first, then label or word-start matches, then other substring matches, so "AI" leads with artificial intelligence

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eurlex_query_sparql _tool

• Read-only SELECT only — update forms and ASK/CONSTRUCT/DESCRIBE are rejected before execution; cdm:, skos:, and xsd: prefixes are auto-injected
• Results capped at 100 rows; optional timeout_hint (1000–55000 ms) under the endpoint's 60-second hard limit
• A zero-row result whose query has an untyped string literal as a triple object carries a notice to type it (^^xsd:string, ^^xsd:anyURI for an ELI) or language-tag it; the query itself is sent unchanged
• Typed errors: not_read_only (a SPARQL Update), unsupported_query_form (ASK, CONSTRUCT, DESCRIBE, or no SELECT), sparql_error, sparql_timeout

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eurlex://document/{celexNumber} _resource

• Metadata snapshot as application/json — resource type, author institution(s) labelled as eurlex_get_document labels them, Advocates General, date, English title, in-force flag, legal basis, EuroVoc subjects; a consolidated text adds base_act_celex and reads authors, in-force flag, legal basis, and subjects from that act
• celexNumber comes from eurlex_search_documents, eurlex_get_cases, or eurlex_lookup_celex

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eurlex://document/{celexNumber}/relations _resource

• One-hop relationship summary — amendment chain, consolidations, national transposition (each measure's related_member_state included), legal basis, citations — each related work with its related_date and English related_title where it has them, capped at 25 per relation type and direction, keeping the newest
• truncated plus a continuation pointer to eurlex_get_relations when more relations exist

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eurlex_comparative_analysis _prompt

• Arguments: domain required; focus optional, folded into its matching analysis axis or added as its own section
• Returns a research plan chaining eurlex_browse_subjects → eurlex_search_documents → eurlex_get_document → eurlex_get_relations for the EU side and courtlistener_search_opinions for the US side, plus a six-axis analysis framework

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Features

Built on @cyanheads/mcp-ts-core: stdio and Streamable HTTP transports, pluggable auth (none / jwt / oauth), swappable storage (in-memory, filesystem, Supabase, Cloudflare KV/R2/D1), structured logging with optional OpenTelemetry tracing.

EUR-Lex-specific:

• No API key required — CELLAR SPARQL and the EUR-Lex REST content endpoints are both publicly accessible
• SPARQL is POSTed with CDM prefix declarations built in; server-side LIMIT enforcement (max 100) guards against Virtuoso timeouts
• Act text is fetched via CELLAR content negotiation (/resource/celex/{CELEX}); HTML passes through as served; Formex4 XML passes through for a single-part act and is assembled into one document from the parts of a multi-part act (HTTP 300 streams) or a zipped Formex package; Markdown is converted server-side
• Virtuoso errors (HTTP 200 with a Virtuoso 37000 Error body) are classified and re-raised as ServiceUnavailable or ValidationError
• Automatic English fallback when a requested translation is unavailable, with requested/effective language reported

Agent-friendly output:

• EuroVoc prerequisite guidance in server-level instructions — agents are directed to eurlex_browse_subjects before concept-filtered searches
• eurlex_lookup_celex confirms CELEX/ELI/ECLI existence upfront, preventing downstream errors in document or relation fetches
• content_status, content_unavailability_reason, and requested/effective language fields distinguish skipped, available, absent, upstream-failed, and incomplete content without string parsing
• Typed reason codes on every tool's error contract let agents branch on outcomes programmatically

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Getting started

Public Hosted Instance

A public instance is available at https://eur-lex.caseyjhand.com/mcp — no installation required. Point any MCP client at it via Streamable HTTP:

{
  "mcpServers": {
    "eur-lex-mcp-server": {
      "type": "streamable-http",
      "url": "https://eur-lex.caseyjhand.com/mcp"
    }
  }
}

Self-Hosted / Local

Add the following to your MCP client configuration file. No API key is required.

{
  "mcpServers": {
    "eur-lex-mcp-server": {
      "type": "stdio",
      "command": "bunx",
      "args": ["@cyanheads/eur-lex-mcp-server@latest"],
      "env": {
        "MCP_TRANSPORT_TYPE": "stdio",
        "MCP_LOG_LEVEL": "info"
      }
    }
  }
}

Or with npx (no Bun required):

{
  "mcpServers": {
    "eur-lex-mcp-server": {
      "type": "stdio",
      "command": "npx",
      "args": ["-y", "@cyanheads/eur-lex-mcp-server@latest"],
      "env": {
        "MCP_TRANSPORT_TYPE": "stdio",
        "MCP_LOG_LEVEL": "info"
      }
    }
  }
}

Or with Docker:

{
  "mcpServers": {
    "eur-lex-mcp-server": {
      "type": "stdio",
      "command": "docker",
      "args": [
        "run", "-i", "--rm",
        "-e", "MCP_TRANSPORT_TYPE=stdio",
        "ghcr.io/cyanheads/eur-lex-mcp-server:latest"
      ]
    }
  }
}

For Streamable HTTP, set the transport and start the server:

MCP_TRANSPORT_TYPE=http MCP_HTTP_PORT=3010 bun run start:http
# Server listens at http://localhost:3010/mcp

Prerequisites

• Bun v1.4.0 or higher (or Node.js v24+).
• No API key needed — EUR-Lex and CELLAR are publicly accessible.

Installation

1. Clone the repository:

git clone https://github.com/cyanheads/eur-lex-mcp-server.git

2. Navigate into the directory:

cd eur-lex-mcp-server

3. Install dependencies:

bun install

4. Configure environment (optional):

cp .env.example .env
# All server-specific vars have sensible defaults — no required vars

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Configuration

All configuration is validated at startup via Zod schemas in src/config/server-config.ts.

Variable	Description	Default
CELLAR_SPARQL_ENDPOINT	CELLAR SPARQL endpoint URL override (e.g., for a local Virtuoso mirror).	http://publications.europa.eu/webapi/rdf/sparql
EURLEX_CONTENT_BASE_URL	EU Publications Office CELLAR content resolver base URL override.	http://publications.europa.eu
SPARQL_QUERY_TIMEOUT_MS	Client-side timeout for SPARQL requests in milliseconds.	55000
MAX_SPARQL_RESULTS	Enforced ceiling on LIMIT in all generated SPARQL queries.	100
MCP_TRANSPORT_TYPE	Transport: stdio or http.	stdio
MCP_HTTP_PORT	Port for HTTP server.	3010
MCP_AUTH_MODE	Auth mode: none, jwt, or oauth.	none
MCP_SESSION_MODE	Session handling: stateful, stateless, or auto (auto resolves to stateful).	stateless
MCP_LOG_LEVEL	Log level (RFC 5424).	info
LOGS_DIR	Directory for log files (Node.js only).	<project-root>/logs
OTEL_ENABLED	Enable OpenTelemetry instrumentation.	false

See .env.example for the full list of optional overrides.

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Running the server

Local development

• Build and run:

  # One-time build
  bun run rebuild
  
  # Run the built server
  bun run start:stdio
  # or
  bun run start:http
  

• Run checks and tests:

  bun run devcheck   # Lint, format, typecheck, security
  bun run test       # Vitest test suite
  bun run lint:mcp   # Validate MCP definitions against spec
  

Docker

docker build -t eur-lex-mcp-server .
docker run --rm -p 3010:3010 eur-lex-mcp-server

The Dockerfile defaults to HTTP transport, stateless session mode, and logs to /var/log/eur-lex-mcp-server. OpenTelemetry peer dependencies are installed by default — build with --build-arg OTEL_ENABLED=false to omit them.

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Project structure

Directory	Purpose
src/index.ts	createApp() entry point — registers tools, resources, and prompts; initializes services.
src/config	Server-specific environment variable parsing and validation with Zod.
src/services/cellar-sparql	CELLAR SPARQL service — POST client, binding mapper, LIMIT enforcement, CDM PREFIX declarations.
src/services/eurlex-content	CELLAR content service — content-negotiation GET client for /resource/celex/{CELEX} (Accept / Accept-Language) with English language fallback, and an in-process cache of served bodies so paging an act fetches it once.
src/mcp-server/tools	Tool definitions (*.tool.ts). Seven tools across document search, retrieval, resolution, case law, relations, EuroVoc, and raw SPARQL.
src/mcp-server/resources	Resource definitions (*.resource.ts). Metadata and relations resources.
src/mcp-server/prompts	Prompt definitions (*.prompt.ts). Comparative analysis prompt.
tests/	Unit and integration tests mirroring src/.

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Development guide

See CLAUDE.md for development guidelines and architectural rules. The short version:

• Handlers throw, framework catches — no try/catch in tool logic
• Use ctx.log for request-scoped logging, ctx.state for tenant-scoped storage
• Register new tools and resources via the barrels in src/mcp-server/*/definitions/index.ts
• Wrap external API calls: validate raw → normalize to domain type → return output schema; never fabricate missing fields

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Contributing

Issues are welcome. Run checks and tests before submitting:

bun run devcheck
bun run test

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License

Apache-2.0 — see LICENSE for details.