sn-mcp-server - Supernova Cosmology MCP Server

MCP server for Type Ia supernova cosmology on public Hubble diagrams: Pantheon+, DES-SN5YR, Union3/UNITY1.5 (+ optional DES-Dovekie). It fetches tidy Hubble diagrams with their full stat+sys covariance, plots them, bins them, fits flat LCDM / wCDM / w0waCDM with the absolute-magnitude/H0 offset marginalised analytically, draws 68/95% contours and compares samples. Part of the cosmo-*-mcp-server family (see docs/CONVENTIONS.md).

Install / run

uv venv --python 3.12 .venv && uv pip install --python .venv/bin/python -e ".[dev]"
.venv/bin/python -m mcp_server --transport stdio
.venv/bin/python -m mcp_server --transport streamable-http --port 8010   # family default port for sn

Related MCP server: pwn-mcp-server

Tools

Likelihood

chi2 = r^T C^-1 r - (1^T C^-1 r)^2 / (1^T C^-1 1), r = mu_obs - mu_th(z_HD, z_hel), with C the full stat+sys covariance (the Pantheon+/DES/cobaya convention for marginalising M over a flat prior). D_L = (1 + z_hel) D_M(z_HD); distances by numerical integration (radiation neglected, < 1e-4 mag; tested against astropy.cosmology).

Sanity checks (flat LCDM, SN only)

wCDM: Pantheon+ w = -0.91 +- 0.15 (pub. -0.90 +- 0.14); DES-SN5YR w = -0.81 +- 0.15 (pub. -0.80 +0.14/-0.16).

Skills

sn-tour, hpc-dispatch-handoff, reproduce-pantheon-plus-om, sn-dark-energy-w0wa.

Data

Small Hubble-diagram tables are bundled (0.8 MB, provenance in data/README.md); covariances (6-33 MB) download on first use into ~/.cache/cosmo-mcp/sn-mcp-server.

Tests

MPLBACKEND=Agg .venv/bin/python -m pytest -q (network tests download the covariances once; deselect with -m "not network"), .venv/bin/python tests/smoke_server.py.