Index Constituents MCP Server

@pipeworx/index-constituents

Current constituents, weights and sectors of six major US and developed-markets equity indexes, plus a dated history of S&P 500 additions and removals — point-in-time index membership built from a live ETF proxy, not a licensed index feed.

Part of Pipeworx — an MCP gateway connecting AI agents to 1779+ live data sources. This is an independent, unofficial integration — not affiliated with, endorsed by, or published by the upstream provider.

Tools

• index_constituents(index, limit?, offset?, sector?) — current equity constituents of one index (sp500, sp400, sp600, russell1000, russell2000, eafe): ticker, name, GICS sector, weight, and the fund's "as of" date. Sorted by weight descending. Cash/collateral/futures the tracking ETF also holds are excluded here (see ishares_etf_holdings). Default limit is 50; pass limit: 600 (the max) to get the whole index in one call — a ~503-row S&P 500 answer is available on request, not by default.
• ishares_etf_holdings(ticker, limit?, offset?, asset_class?) — every reported position of one of the six tracking ETFs (IVV, IJH, IJR, IWB, IWM, EFA), including cash, collateral and futures, each labeled with its own asset_class so they are never silently folded in with equities.
• constituent_changes(index, from?, to?, limit?) — dated S&P 500 adds and removes (index must be sp500; the other five indexes have no public, dated changes table). from/to accept a bare year ("2024") or an ISO date.

Auth

Keyless. Both upstreams are public, unauthenticated pages.

Data sources

• iShares (BlackRock) — the daily holdings file each fund publishes for its own index-tracking ETF (IVV/S&P 500, IJH/S&P MidCap 400, IJR/S&P SmallCap 600, IWB/Russell 1000, IWM/Russell 2000, EFA/MSCI EAFE). This is a PROXY for official index membership, not the index provider's own data: S&P and Russell do not publish their constituent files for free, so the fund's actual reported portfolio — which tracks its index closely — is the nearest public point-in-time stand-in. Weights are the ETF's own portfolio weights, not S&P/Russell's published index weights, and can differ slightly (cash drag, sampling, corporate-action timing).
• Wikipedia — "List of S&P 500 companies" and "Historical components of the S&P 500" (the latter is this pack's source for constituent_changes: a community-maintained, citation-backed table of every S&P-announced S&P 500 swap since 1963, with its effective date and stated reason).

Reuse note (checked 2026-10-12). BlackRock's site terms (blackrock.com/corporate/compliance/terms-and-conditions) say website content is "solely for your personal, non-commercial use" and may not be "distribute[d], modif[ied], transmit[ted], reuse[d], repost[ed]... for public or commercial purposes... without BlackRock's written permission." This pack does not store, mirror or redistribute the holdings file: every call fetches the fund's current file live (cached at the edge for a day, the same way a normal browser would cache it) and returns the parsed rows for that one call. Per the proxy-vs-mirror rule (CLAUDE.md, fleet #1389 — "a live upstream call per request needs no explicit grant; only bulk-copying/mirroring does"), that is proxying, not redistribution; no dataset is baked into this pack or into Pipeworx's own storage. Wikipedia's content is CC BY-SA 4.0, which permits reuse including attribution-carrying commercial reuse — source on every response names Wikipedia and the page.

Notes

• The iShares holdings file's column layout is not identical across funds: IJH and IJR add a "Type" column and call the weight field "Market Weight" instead of "Weight (%)". This pack reads the header by NAME, not by position, so a reordered column does not silently misalign the data.
• data_as_of on every response is the fund's own "Fund Holdings as of" date from the file, not the time Pipeworx fetched it — use it to judge freshness.
• The S&P 500 holdings file carries a handful of non-equity rows (cash, collateral, a futures contract used to stay fully invested between rebalances) even though the fund is "all-equity" by mandate; these are excluded from index_constituents and labeled plainly in ishares_etf_holdings.
• constituent_changes only covers sp500 today. The other five indexes have no equivalent free, dated, citation-backed changes table — adding one would mean a different, likely paid, source.

Quick Start

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

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

What this endpoint actually serves

tools/list at https://gateway.pipeworx.io/index-constituents/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 1779+ 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/index_constituents \
  -H 'Content-Type: application/json' \
  -d '{"index":"sp500","limit":600}'

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

Standalone (no gateway account)

This package also runs as a local stdio MCP server — no Pipeworx account, no gateway round-trip:

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

Or run it directly to confirm it starts:

npx -y @pipeworx/mcp-index-constituents

It speaks MCP over stdin/stdout and answers initialize/tools/list/tools/call for only this pack's tools — none of the shared meta-tools the gateway connection above adds. Same source, same tools, no ask_pipeworx routing.

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 Index Constituents data" })

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

More

• Docs and guides
• pipeworx.io

License

MIT