io.github.cyanheads/eur-lex-mcp-server

@cyanheads/eur-lex-mcp-server

Search EU legislation, CJEU case law, and treaties; traverse the CELLAR relationship graph; resolve EuroVoc concepts via MCP. STDIO or Streamable HTTP.

7 Tools • 2 Resources • 1 Prompt

Public Hosted Server: https://eur-lex.caseyjhand.com/mcp

Overview

EU legislation, CJEU case law, and treaties from EUR-Lex. Search documents and case law, fetch full text, resolve citations, trace how acts amend and cite each other, and browse the EuroVoc subject thesaurus.

Tools

Resources

All resource data is also reachable via tools.

Prompts

Capability reference

eurlex_search_documents tool

• At least one filter: keyword (English titles, plus CELEX numbers or fragments such as 2016R0679; a keyword with letters and no digit, such as R(01), scans every CELEX and can take tens of seconds; no body search), document_type (REG, DIR, DEC, TREATY, JUDG, OPIN_AG, PROP, REC), 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eurovoc_concept (from eurlex_browse_subjects), author_institution, or in_force (true/false; false covers repealed, expired, and not-yet-in-force acts)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 (a larger limit is served at 100 and reported in limit_clamp), newest first; each row flags is_consolidated and is_corrigendum, and corrigenda and consolidated texts appear only under include_corrigenda and include_consolidated. Paging stops at row 10,000: the last page carries no next_offset and a notice giving the date_from/date_to window that continues past it
• No match returns an empty page with a notice on how to broaden the filters; typed errors: no_filters, invalid_date_range, invalid_author_institution and invalid_keyword (no letters or digits), offset_past_window (offset 10,000 or more)
• author_institution matches English authority labels and national-court names returned by eurlex_get_document, such as European Parliament or Supremo Tribunal de Justiça, with or without date bounds

eurlex_get_document tool

• Exactly one of celex_number, eli_uri, or work_uri (pasted forms such as a CELEX: prefix or EUR-Lex URL are accepted); body as html (default), markdown, or xml (Formex4) in any of the 24 EUR-Lex languages, falling back to English. Case law also carries ecli, formation, referring_court, subject_matter, and case_reference; a consolidated text reports its base act as base_act_celex
• content_mode "paged" (default), "full", or "metadata_only", capped at 100,000 characters per call (a larger limit is reported in limit_clamp) with content_chars_total/has_more to page on; outline: true lists headings with offsets, and select (e.g. { articles: "1,5,17" }) returns just those sections. For judgments and AG opinions the outline lists section headings, and select: { operative_part: true } returns the ruling alone
• is_superseded flags a newer consolidated version (current_consolidated_celex, consolidated_as_of), and resolve: "current_consolidated" serves it; in_force: false comes with repealed_by, end_of_validity, or entry_into_force where CELLAR records one. Typed errors: invalid_identifier_args, not_found, content_challenge (a WAF bot-challenge in place of text)
• Available legacy HTML/Markdown bodies may carry content_omissions: { tables }: missing-table markers counted across the full source, including outside the returned window. Paging cannot recover these tables. alternative_representations lists PDF streams advertised for the served work and language when discovery succeeds; XML availability remains independent. Metadata-only calls do not inspect source omissions
• National implementing measures carry sparse national_measure citation fields: journal, number, pages, publication_date, and notification_date, including metadata-only calls. Numbers and pages retain their source spelling; publication, notification, and document dates are distinct. When the body is unavailable, use the gazette citation to retrieve it; no national-portal URL is inferred, and notification does not prove complete transposition

eurlex_lookup_celex tool

• A CELEX number, ELI URI, ECLI, or OJ citation naming its act type and year (Regulation (EU) 2016/679, Directive 95/46/EC); pasted forms (a CELEX: prefix, a EUR-Lex page URL, an ELI with or without scheme or language segment) are normalized and echoed in celex_number. 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; ambiguous_identifier fires when auto-detection can't classify the input. A case number (C-131/12) returns found: false with a notice pointing to eurlex_get_cases
• Returns work URI, confirmed CELEX number, resource type, date, and the case's ECLI; found: false with a notice for a well-formed identifier that matches no work

eurlex_get_cases tool

• Filters: case_number (C-131/12, T-22/20, F-12/05, or a pre-1989 26/62; reaches every judgment, order, and AG opinion filed under it), court (CJEU or GC), case_type (judgment, order, ag_opinion), keyword (English titles, plus CELEX numbers or fragments such as 2013CJ0131), 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 (a larger limit is served at 100 and reported in limit_clamp), newest first; each case carries its ECLI where recorded, plus formation, advocate_general, display_title, parties, referring_court, subject_matter, and case_reference, and the raw title only when those fields miss part of it. Paging stops at row 10,000: the last page carries no next_offset and a notice giving the date_from/date_to window that continues past it
• No match returns an empty page with a notice on how to broaden the filters; typed errors: invalid_case_number, invalid_date_range, invalid_keyword (no letters or digits), offset_past_window (offset 10,000 or more)
• case_type: "ag_opinion" includes Advocate General opinions (OPIN_AG) and views (VIEW_AG); resource_type distinguishes AG Opinion from AG View

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, basis_for, interprets, interpreted_by, consolidated_version, national_transposition (omit for all)
• basis_for lists the works naming the act among their legal bases; interpreted_by lists the CJEU and General Court rulings interpreting it, and interprets what a ruling interprets. member_states narrows national_transposition to named member states (ISO 3166-1 alpha-3 or two-letter codes, echoed as alpha-3); using it without national_transposition fails as member_states_not_applicable
• One hop, paged per relation type and direction via offset/limit (up to 100, default 100; a larger limit is reported in limit_clamp), newest first. Each type and direction pages to row 10,000, then a notice routes older works to eurlex_query_sparql with a ready-to-run query
• Each complete response surface is budgeted independently at 64,000 UTF-8 bytes, including JSON and enrichment. Oversize pages retain the largest common per-type/direction depth that fits, with whole rows and titles; the notice gives requested/applied limits and rows withheld. Continue at next_offset (the current offset plus the applied depth). A depth-1 page is returned whole even if it exceeds the budget, with disclosure. Fitting pages are unchanged; omitting relation_types equals listing all thirteen types
• Each relation carries relation_type, direction (outgoing/incoming), related_work_uri, and where known related_celex_number, related_date, related_title (English only), and related_member_state on national_transposition rows; empty_relation_types separates "no edges of this type" from "paged out". Typed errors: invalid_identifier_args, member_states_not_applicable, not_found, offset_past_window

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 (up to 50; a larger limit is served at 50 and reported in limit_clamp), to row 10,000 (offset_past_window beyond)
• 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

eurlex_query_sparql tool

• Read-only SELECT only (update forms and ASK/CONSTRUCT/DESCRIBE are rejected); cdm:, skos:, and xsd: prefixes are auto-injected; optional timeout_hint (1000–55000 ms)
• Results capped at MAX_SPARQL_RESULTS (default 100); a truncated result's notice says to add ORDER BY and repeat with a higher OFFSET, up to row 10,000. A zero-row result from an untyped string literal gets a notice to type it (^^xsd:string, ^^xsd:anyURI for an ELI) or language-tag it
• Typed errors: not_read_only (a SPARQL Update), unsupported_query_form (ASK, CONSTRUCT, DESCRIBE, or no SELECT), sparql_error, sparql_timeout

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

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

• One-hop relationship summary over every eurlex_get_relations type, each related work with its related_date and English related_title where it has them, capped at 25 per relation type and direction (newest kept)
• truncated plus a continuation pointer to eurlex_get_relations when more relations exist

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 that restates the domain in EU legal vocabulary ("antitrust" → "competition law"), chains 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

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; HTML passes through as served, multi-part Formex4 XML is assembled into one document, and Markdown is converted server-side
• Syntax, compile, and sort-window errors fail at once as sparql_error (a sort-window error, SR353, hints to lower OFFSET or narrow the query) and timeouts as sparql_timeout, neither retried; gateway pages and other transient failures are retried
• 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

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

1. Navigate into the directory:

cd eur-lex-mcp-server

1. Install dependencies:

bun install

1. Configure environment (optional):

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

Configuration

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

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

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.

Project structure

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

Contributing

Issues are welcome. Run checks and tests before submitting:

bun run devcheck
bun run test

License

Apache-2.0 — see LICENSE for details.