Cern Opendata MCP Server

@cyanheads/cern-opendata-mcp-server Search CERN Open Data, fetch records, files, analysis environments, CMS good-run lists, HLT paths via MCP. STDIO or Streamable HTTP. 7 Tools • 1 Record Resource • 1 Agent Skill

Public Hosted Server: https://cern-opendata.caseyjhand.com/mcp

Overview

Particle-physics data from the CERN Open Data Portal: collision and simulated datasets, analysis software, and documentation from ALICE, ATLAS, CMS, LHCb, and more. Search with live facet counts, open records with license and citation, list data files, assemble a record's analysis environment, and look up CMS good-run lists and trigger paths. Runs as a stdio process, a local Streamable HTTP server, or the public hosted endpoint above.

Tools

Resources

Tool-only clients get the same data from cern_opendata_get_records.

Agent skill

cern-opendata-guide connects dataset discovery, file indexes, analysis environments, CMS certification and trigger evidence. It covers identifier sources and checks to make before treating a result as complete. The guide ships with plugin installs, npm, Docker and the Claude Desktop bundle. MCP clients can discover it through the Skills extension and its SDK-generated skill resources, alongside the record resource above. No prompts are registered.

Capability reference

cern_opendata_search_records tool

• Optional query (an OpenSearch query_string, up to 500 characters) plus OR-list filters type, experiment, category (physics category, Higgs Physics::Standard Model), keywords, collision_energy, collision_type, file_type, availability, collection, and the LHCb magnet_polarity, stripping_stream and stripping_version, each an array of values; year_from/year_to and min_events/max_events bound the data-taking year and event count
• sort (bestmatch, mostrecent for newest date_published first, title, title_desc), limit 1–50 (default 10; a larger value, up to 10,000, is served at 50 with a notice) and page from 1, counting pages of the limit applied; page × limit past 10,000 fails as page_window_exceeded
• Compact hits with recids, plus thirteen live facets that each ignore their own filter (type and category with up to 10 secondary values each, and subtypes_other_count or subcategories_other_count when the portal cuts that list); applied_filters echoes what ran, and values outside the verified vocabulary appear under unrecognized_values

cern_opendata_get_records tool

• ids: up to 100 recids, DOIs, CMS dataset paths (/Primary/Era/TIER) or documentation slugs, mixed in one array; the first 20 distinct are looked up and the rest returned in deferred
• Each record carries a license with its basis (record, cern_terms_default, not_stated) and, when it has a DOI, a ready citation
• Documentation and news bodies come in slices of up to 30,000 characters: body_offset with that one id reads on from the body_next_offset the last slice returned
• Each response stays within 64,000 bytes, except that the first record always comes back whole: records past the budget are left out and listed in deferred, ahead of any ids past the first 20, to pass back as ids
• Records also return what they state of a variables dictionary (name, type, unit, description), a physics category, pile-up (pileup_html, with the pile-up datasets under links), keywords, and the LHCb magnet_polarity and stripping stream and version
• Unresolved identifiers land in missing with interpreted_as and guidance instead of failing the call; file lists come from cern_opendata_list_files

cern_opendata_list_files tool

• recid required; without index, returns the record's file indexes and regular files, and with an index key, that index's files, read without the rest of the record
• limit 1–500 (default 50; a larger value, up to 10,000, is served at 500 with a notice), continued with next_cursor; each file carries xrootd_uri, size_in_bytes, checksum and availability, an https_url when one can be built from its key or EOS path, and key or filename as the portal states them, and each index a uri_list_url listing every XRootD URI in it
• Files marked on demand sit on tape and must be requested on the record's portal page first; an umbrella record with no files of its own returns its child recids under children

cern_opendata_get_analysis_env tool

• recid required; software carries the record's own container images, CMSSW release, global tag and environment recid
• environment_records (condition, VM, validation) for the record's run periods and example_software that declares it works with the record, up to 50 between them; guides quotes the linked section of the first two portal guides, each capped at 12,000 characters, with the [label]: url reference definitions the quote links through from elsewhere in the guide, and a cut names the cern_opendata_get_records body_offset that reads on from it
• Always separately_licensed: true; linked records or guides that can't be read leave a notice instead of failing the call

cern_opendata_get_validated_runs tool

• Exactly one of recid (a CMS collision dataset or a validated-run list) or run_period (Run2012B; 2012B also matches); variant full or muons_only; run_min/run_max; limit 1–2000 (default 200; a larger value, up to 10,000, is served at 2000 with a notice)
• A dataset recid bounds the runs to the dataset's first and last listed run, echoed in run_bounds; when several lists match, matched_lists names them and no runs are read
• Each run carries lumi_sections and lumi_ranges; list.https_url downloads the whole list file. CMS only: other records fail as no_validated_runs

cern_opendata_search_trigger_paths tool

• path: an exact name (HLT_IsoMu24, AlCa_EcalPi0) or a prefix with one trailing * (HLT_IsoMu*); a name without the HLT_ prefix is matched against record path names in the case given and also searched with HLT_ added, and a _v version suffix is dropped; optional year, limit 1–50 (default 10; a larger value, up to 10,000, is served at 50 with a notice) and page
• Each per-year record is parsed into the primary datasets its title names, first_seen, last_seen, per-version run ranges with their l1_seed, and HLT menu record links; parsed: false marks a record to read from its abstract_html
• CMS open data from 2011–2016 only

cern_opendata_list_reference tool

• Optional topic: experiments, record_types, collision_energies, collision_types, file_types, availability, categories, lhcb, identifiers, query_syntax, licensing or run_periods; omit it for every table
• Static and offline; categories, lhcb and run_periods are dated snapshots, while the search facets and cern_opendata_get_validated_runs read the live portal

cern-opendata://record/{recid} resource

• One record by recid (6004, or a prefixed recid such as atlas-160006; leading zeros ignored) as application/json, in the cern_opendata_get_records record shape: metadata (variable dictionary, physics category, pile-up and LHCb run conditions included), license and citation, without file lists
• recid comes from cern_opendata_search_records; reads carry a 15-minute public cache hint

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.

CERN Open Data-specific:

• Keyless and read-only; it never stages tape files or writes anything
• One shared pacer at 50 requests a minute, under the portal's published 60 per client IP, and one 50-second deadline per call across queue wait and retries
• Filter values canonicalized against the portal's verified vocabulary (13 tev → 13TeV, lhcb → LHCb, Pb-Pb → PbPb, dataset/collision → Dataset::Collision); unknown values are sent as given and flagged
• Tape-resident (ondemand) records are included in every search and lookup, where the portal othe