pairbook-mcp
MCP server and CLI for PairBook, the correlation and ETF-overlap engine covering 4,700+ US stocks and ETFs. Any of the 11.3 million possible pairs can be compared: 52,000+ popular pairs come precomputed with issuer-sourced holdings overlap, and every other combination is computed on demand from weekly return series. The underlying JSON API is free and static, needs no key, and refreshes every trading day after the US close.
Ask your AI assistant things like "how correlated are QQQ and VOO, and how much do they overlap?" or "find me diversifiers for NVDA" and it can answer with fresh, sourced numbers instead of guessing.
MCP setup
Claude Code
claude mcp add pairbook -- npx -y pairbook-mcp
Cursor: one-click install with
Claude Desktop: add this to claude_desktop_config.json:
{
"mcpServers": {
"pairbook": {
"command": "npx",
"args": ["-y", "pairbook-mcp"]
}
}
}
Any other MCP client works the same way: run npx -y pairbook-mcp over stdio.
Tools
| Tool | What it answers |
|---|---|
compare_pair |
Correlation (1/3/5y, weekly), covariance, beta vs S&P 500, volatility and holdings overlap for two assets |
symbol_profile |
One asset: beta, volatility, returns, most correlated assets |
find_diversifiers |
Lowest/most negative 3-year correlations to a given asset |
weekly_returns |
Weekly return series (up to 156 weeks) for custom math |
resolve_symbol |
"nvidia" → NVDA across the covered universe |
CLI
The same data in your terminal, no install needed:
npx -y -p pairbook-mcp pairbook QQQ VOO
or after npm i -g pairbook-mcp:
pairbook QQQ VOO # compare two assets
pairbook NVDA # one asset's profile
pairbook search nvidia # find a ticker
pairbook AAPL MSFT --json
Exit codes: 0 on success, 1 on any error (errors go to stderr). --json prints one valid JSON document on stdout, so pairbook qqq voo --json | jq .correlation_weekly just works.
DGRO vs SCHD (data as of 2026-08-27)
correlation 1y 0.74 3y 0.88 5y 0.93
beta vs SPY DGRO 0.65 SCHD 0.52
volatility DGRO 11.4% SCHD 12.9%
overlap 20.8% across 32 common holdings (issuer files 2026-08-26)
https://www.pairbook.io/pair/dgro-vs-schd/
Scope
PairBook is a specialist: correlation, overlap and diversification structure. It pairs well with a general market-data MCP server that brings quotes, fundamentals and news, so install both and let your assistant combine them.
Data
Everything comes from the free PairBook API: correlations computed on weekly returns (1/3/5-year windows), overlap from issuer portfolio disclosures, recomputed every trading day. The dataset is also published as CSV downloads with a DOI.
Free with attribution (a link back to pairbook.io). US-listed stocks and ETFs only. Nothing here is investment advice.
Privacy
The server and CLI run entirely on your machine and are read-only. They call a single host (www.pairbook.io) to fetch public market data, identify themselves with a version and surface string in the user agent, and send nothing else: no prompts, no conversation content, no personal data, no telemetry. Full policy: pairbook.io/privacy.
License
MIT © VoidLab
