ISRCTN — UK-Based International Clinical Trial Registry

ISRCTN (isrctn.com) is a primary clinical trial registry recognised by WHO and ICMJE, operated by Springer Nature/BMC. It covers UK and international trials — including many non-US studies that never appear on ClinicalTrials.gov — and assigns a permanent ISRCTN number to every registered study. Free, keyless, public XML query API.

Part of Pipeworx — an MCP gateway connecting AI agents to 1865+ live data sources. This is an independent, unofficial integration — not affiliated with, endorsed by, or published by the upstream provider.

Why this matters for AI agents

ClinicalTrials.gov is US-centric. A question like "what trials exist on psilocybin for stroke recovery" is only half-answered without ISRCTN, since several UK/EU-sponsored studies register here instead of (or in addition to) ClinicalTrials.gov. Use this pack alongside clinicaltrials for international coverage, not in place of it.

Two flows:

1. Search. "Studies on X and Y" → isrctn_search({query: "psilocybin depression"}) or, to require BOTH a registered condition and a registered intervention, isrctn_search({condition: "stroke", intervention: "psilocybin"}). Combining condition and intervention is an AND, not an OR — a real zero means no ISRCTN trial currently pairs that condition with that intervention, and the response echoes query_used so the caller can see exactly what was searched.

2. Single record. isrctn_trial({id: "ISRCTN37167117"}) → full structured record: title, condition(s), intervention(s)/phase, sponsor, funder, dates, countries, and whether a results report has been posted.

Related MCP server: ClinicalTrials.gov MCP Server

Status is DERIVED, not a registry field

ISRCTN's XML feed carries no "overall trial status" string — unlike ClinicalTrials.gov. Every returned trial computes status from its recruitment-window dates (recruitment_start, recruitment_end, overall_end_date) relative to the current date, and status_basis names exactly which date drove the call (e.g. "overall trial end date (2025-01-23T00:00:00.000Z) has passed"). isrctn_search's status filter matches against this derived value and is applied client-side over a fetched batch (status_filter_scanned reports how many trials were scanned), since the upstream has no server-side status field to filter on.

Search syntax

query is free text (ISRCTN's search is a Lucene index over the full record — title, summary, eligibility criteria, etc.). Multiple words are ANDed by default ("psilocybin depression" matches trials containing both terms, not either), confirmed against the live API: psilocybin depression and psilocybin AND depression return identical counts, "psilocybin depression" (a phrase) returns zero. condition and intervention match ISRCTN's indexed condition: / intervention: fields specifically — these are narrower than a free-text match on the same word (e.g. condition:stroke returns ~1/4 the hits of a bare stroke search, because it excludes trials that only mention "stroke" in eligibility criteria or elsewhere).

At least one of query, condition, intervention is required.

Auth

Keyless. Public, unauthenticated XML query API.

Data sources

• https://www.isrctn.com/api/query/format/default?q={lucene_query}&limit={n} — search (e.g. q=psilocybin+depression&limit=10); also used for single-record lookup (isrctn_trial queries by the canonical ISRCTN37167117-shaped id with limit=1).

Notes for the next person

• The single-record URL shape /api/query/ISRCTN37167117/format/default documented informally elsewhere 404s live (verified 2026-10-09) — the working path for one record is the SAME search endpoint, queried by id.

• A non-existent ISRCTN id returns HTTP 200 with an empty allTrials element (totalCount of zero) — a legitimate empty result, surfaced as {found: false}, not an error.

• A malformed Lucene query (e.g. unbalanced quotes) also silently returns totalCount="0" rather than an HTTP error — user input going into query, condition, and intervention is Lucene-escaped before being sent, so a caller's literal text (parentheses, colons, quotes) can't accidentally produce a false zero from broken query syntax.

• A response that is HTTP 200 but has no allTrials/totalCount root element, or that claims totalCount > 0 with zero parseable fullTrial blocks, is thrown as a loud upstream_parse error — never silently returned as an empty result.

Quick Start

Add to your MCP client (Claude Desktop, Cursor, Windsurf, etc.):

{
  "mcpServers": {
    "isrctn": {
      "url": "https://gateway.pipeworx.io/isrctn/mcp"
    }
  }
}

What this endpoint actually serves

tools/list at https://gateway.pipeworx.io/isrctn/mcp returns the tools in the table above plus the shared Pipeworx meta-tools — ask_pipeworx, discover_tools, search_within, remember/recall and the rest of the gateway-wide set. So the tool count you see is larger than this table: a single-pack endpoint currently lists roughly 30 shared tools alongside the pack's own. The connection's initialize response states its exact scope, and is the authoritative answer for a given day.

This is deliberate, not multiplexing by accident. The meta-tools are what let a scoped connection answer a question this pack does not cover — via ask_pipeworx, which routes across the whole catalog — without you adding a second MCP server. There is currently no way to mount a pack endpoint without them; if the extra schemas cost you more context than the routing is worth, connect to the full gateway once rather than to several pack endpoints.

Or connect to the full Pipeworx gateway to get every pack's tools listed directly, instead of just this one's:

{
  "mcpServers": {
    "pipeworx": {
      "url": "https://gateway.pipeworx.io/mcp"
    }
  }
}

Both URLs reach the same gateway and the same 1865+ data sources. The only difference is which pack's tools are listed directly; ask_pipeworx reaches all of them from either one.

No MCP client? Call it over HTTP

curl -X POST https://gateway.pipeworx.io/v1/tools/isrctn_search \
  -H 'Content-Type: application/json' \
  -d '{"query":"psilocybin depression","limit":5}'

No account needed for the first calls. Inspect any tool: GET https://gateway.pipeworx.io/v1/tools/isrctn_search. Find one: POST https://gateway.pipeworx.io/v1/tools/search_packs with {"query":"..."}.

Run it from npm

@pipeworx/mcp-isrctn is a local stdio bridge to the Pipeworx gateway: your MCP client starts it with npx, and it forwards every call to the same https://gateway.pipeworx.io/isrctn/mcp endpoint shown above. It needs network access; there is no offline mode.

{
  "mcpServers": {
    "isrctn": {
      "command": "npx",
      "args": ["-y", "@pipeworx/mcp-isrctn"]
    }
  }
}

Without a key it calls anonymously, capped at 50 calls a day. A free account raises that to 200 a day: get a key at https://pipeworx.io/signup and add "env": { "PIPEWORX_API_KEY": "<your key>" } to the server entry. The key is sent as a Bearer token, the same way a hosted connection sends it, so calls are metered and billed exactly as they are there.

It lists only this pack's tools by default. Set PIPEWORX_META_TOOLS=1 to also list ask_pipeworx and the other gateway-wide tools.

Behind an HTTPS proxy: Node's built-in fetch does not read HTTPS_PROXY by default. Newer Node releases honour it when NODE_USE_ENV_PROXY=1 is set; check your Node version's documentation.

Using with ask_pipeworx

Instead of calling tools directly, you can ask questions in plain English — this works on the pack endpoint above as well as on the full gateway:

ask_pipeworx({ question: "your question about Isrctn data" })

The gateway picks the right tool and fills the arguments automatically.

More

• Docs and guides

• pipeworx.io

License

MIT