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eur-lex-mcp-server

by io.github.cyanheads

Get CELLAR Relationship Graph

eurlex_get_relations
Read-onlyIdempotent

Traverse the one-hop CDM relationship graph of an EU act: what it amends or is amended by, what it repeals or is repealed by (explicit and implicit), its consolidated versions, its legal basis, and works that cite it. Returns direct relations only, paginated per relation type and direction. Requires a CELEX number or CELLAR work URI.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
limitNoMaximum related works per relation type and direction (1–100, default 100). Incoming edges are ordered newest-first, so the cap keeps the newest — page with offset for older ones. When truncated is true, at least one direction filled its cap.
offsetNoPagination offset applied per relation type and direction — related works to skip (default 0). Page forward by adding limit; incoming edges are newest-first, so higher offsets reach older works.
work_uriNoCELLAR work resource URI to traverse (e.g. http://publications.europa.eu/resource/cellar/3e485e15-11bd-11e6-ba9a-01aa75ed71a1). Used directly without CELEX resolution. Provide exactly one of celex_number or work_uri.
celex_numberNoCELEX number of the work to traverse (e.g. 32016R0679). Provide exactly one of celex_number or work_uri.
relation_typesNoSubset of relation types to return; omit for all. Types: cites, amends, amended_by, repeals, repealed_by, implicitly_repeals, implicitly_repealed_by, legal_basis (treaty/article this act rests on), consolidated_version (consolidated texts of this act).

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
capNoThe per-direction cap applied to this page.
errorNoPresent when the call failed. Absent on success.
shownNoNumber of relations returned in this page.
totalNoNumber of relations returned in this page (not a corpus-wide count). A direction that filled its cap sets truncated — page with offset for the rest.
offsetNoPagination offset applied to this response (per relation type and direction).
work_uriNoCELLAR URI of the source work (the work_uri input, or resolved from the CELEX).
relationsNoDirect CDM relations for the requested work.
truncatedNoTrue when at least one relation type/direction filled its per-direction cap and more related works may exist — page with offset.
celex_numberNoCELEX number of the source work whose relations were traversed. Absent when addressed directly by work_uri.
empty_relation_typesNoRequested relation types that returned zero relations in THIS page. Page-scoped: a type can appear here because all its edges sit beyond the current offset/limit window, not only because the act genuinely has none of that relation — so absent-from-here does not prove absent-in-CELLAR. When every requested type is empty the tool throws no_relations instead.
requested_relation_typesNoThe relation types this request traversed — the explicit relation_types list, or all types when it was omitted. Diff against the types present in relations[], or read empty_relation_types, to confirm which requested types returned edges.

TDQS

A4.3/5.0
Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare readOnlyHint=true, openWorldHint=true, and idempotentHint=true. The description adds meaningful behavioral context beyond these: it clarifies that only one-hop direct relations are returned, that pagination is applied per relation type and direction, and that a CELEX or work URI is required for traversal. This adds value without contradicting any annotation.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is two sentences, front-loaded with the core purpose, then the scope constraint. Every clause contributes: it states what relations are covered, that only direct relations are returned, the pagination model, and the identification requirement. No wasted words.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the 5 parameters (all documented in schema) and the existence of an output schema, the description is complete. It states the exact scope (one-hop, direct relations), the relation types available, pagination behavior, and the required input form. An agent has everything needed to call this tool correctly.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 100%, so the baseline is 3. The description itself does not add parameter details beyond what the schema already provides; it only reinforces the mutual exclusivity of celex_number and work_uri, which is also stated in each parameter's description. The schema carries the heavy lifting, so no bonus is warranted.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description opens with a specific verb and resource: 'Traverse the one-hop CDM relationship graph of an EU act' and enumerates the exact relation types (amends, repeals, consolidated versions, legal basis, citations). This is unambiguous and clearly differentiates from sibling tools like eurlex_get_document (fetch full document) or eurlex_search_documents (text search).

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines4/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description gives clear context: it returns direct relations only, is paginated per type/direction, and requires a CELEX number or CELLAR URI. It does not explicitly name alternatives or state when NOT to use it, but the scope statement effectively distinguishes it from siblings. No explicit exclusion is provided, so a 4 is appropriate rather than 5.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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TDQS

A4.4/5.0
Disambiguation5/5

Each tool targets a distinct resource or action: subject browsing, case search, document retrieval, relation traversal, identifier resolution, raw SPARQL, and legislation search. The few potentially similar tools (search_documents vs get_cases) are clearly separated by corpus and description.

Naming Consistency5/5

All tools follow the consistent eurlex_verb_noun pattern in lowercase snake_case, such as eurlex_get_document, eurlex_search_documents, and eurlex_lookup_celex. Verbs vary but the pattern is uniform and predictable.

Tool Count5/5

Seven tools is well-scoped for an EU legal research server covering search, retrieval, relationship traversal, and identifier resolution. Each tool has a clear role and none feel redundant or excessive.

Completeness4/5

The core research workflow is covered: browse subjects, search legislation, search cases, fetch documents, resolve identifiers, and traverse relations. Minor gaps exist such as no full-text body search and no explicit case-law full-text retrieval, but the raw SPARQL escape hatch partially mitigates these.

Resources