Cosine Astro MCP server

by ganguoguo444004-coder·io.github.ganguoguo444004-coder/cosine-astro-mcp·v0.1.0

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Astrology: natal charts, transits, synastry, retrogrades, profections. Computed offline.

A89/100grade A

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Safety scan

A89/100

full report

Adoption

Growing

0 stars47 downloads/wk

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If you have run it, two minutes of your experience saves the next person an afternoon.

Cosine Astro tools (6)

write = sends, deletes, buys or posts

Read from the package source without running it. The installed server may list more.

annual_profection
Hellenistic annual profection for an age or a date: the profected house (whole-sign, counted from the Ascendant; from the Sun's sign if the birth time is unknown), its sign, the lord of the year (traditional ruler, with the modern co-ruler) and where that lord sits in the natal chart, plus the dates the profection year runs.
mercury_retrograde
Mercury retrograde periods overlapping a date range (default: the next 12 months): pre-shadow start, station retrograde, station direct and post-shadow end (to about a minute, in UTC and a chosen time zone), with the degrees and signs of the two stations.
moon_phase
The Moon's phase at a moment (default: now): phase name, illuminated fraction, Sun–Moon angle, days since new moon, the Moon's and Sun's signs, and the next new, first-quarter, full and last-quarter moons.
natal_chart
Cast a tropical natal (birth) chart: the ten planets with sign, degree, house and retrograde flag; Ascendant and Midheaven; twelve house cusps (Placidus by default); major aspects with orbs and applying/separating; and the dominant element and modality. Works without a birth time (no angles or houses then).
synastry
Compare two natal charts: the major aspects between person A's planets (and Ascendant) and person B's, with orbs (conjunction/opposition 6°, square/trine 5°, sextile 3°), where each person's planets fall in the other's houses, and a simple descriptive tally (not a compatibility score).
transits
Planet positions for a date and time (default: now), and, given a natal chart, the major aspects the transiting planets make to the natal planets, Ascendant and Midheaven within an orb (default 2°), with the natal house each transiting planet is passing through.

Public scan report

scanner v0.1.10 · 2026-10-28 · same rubric, same numbers if you re-run it

no findings

Code scan25 source files scanned25/25
–Live reliabilityno gateway calls yet and no remote to proben/a
–Tool poisoningtools not inspected (local package is not executed); not countedn/a
Auth qualitylocal package, no credentials required12/15
Maintenancelast push 11 days ago15/15
Maintainer identityregistry namespace matches repository owner6/10

Overall 89/100. Components that don't apply are left out of the denominator. Any critical finding is an F.Rubric Appeal a finding JSON

How Cosine Astro compares

Against every graded MCP server, from our own scans and uptime checks. Updated after each scan run.

Safety score: 89/100; higher than 80% of 48,255 servers
Tools: 6; the typical server has 7
Tools that change things: 0%; typical: 0%. Fewer write tools means less an agent can break
Downloads a week: 47; more than 39% of 12,191 servers with a package

What its tools let an agent do: 6 read

Install Cosine Astro in Claude Code, Cursor or VS Code

Runs npx -y cosine-astro-mcp on your machine. Read the scan report first; the gateway never runs local packages.

claude mcp add cosine-astro-mcp -- npx -y cosine-astro-mcp

Add to Cursor

What the publisher says

From the Cosine Astro repository's README, as published. We do not edit it. Read it on GitHub

cosine-astro-mcp

An MCP server for Western (tropical) astrology calculations: natal charts, transits, synastry, Mercury retrograde, annual profections and moon phases.

Language models are poor at working out where the planets were on a given date; they tend to guess. This server computes the positions instead, offline, from the astronomy-engine ephemeris, and hands the model both a compact text summary and the full data as JSON. No API keys, no network calls, no accounts.

Made by COSINE 余弦 — cosineastro.com, a birth-chart site with AI readings. This is the same chart engine the site runs, published as an MCP server.

繁體中文說明

Install

Requires Node.js 20 or later.

Claude Code

claude mcp add cosine-astro -- npx -y cosine-astro-mcp

Add --scope user to make it available in every project.

Claude Desktop — edit claudedesktopconfig.json (Settings → Developer → Edit Config):

{
  "mcpServers": {
    "cosine-astro": {
      "command": "npx",
      "args": ["-y", "cosine-astro-mcp"]
    }
  }
}

Cursor — ~/.cursor/mcp.json (global) or .cursor/mcp.json (per project):

{
  "mcpServers": {
    "cosine-astro": {
      "command": "npx",
      "args": ["-y", "cosine-astro-mcp"]
    }
  }
}

Any other MCP client that speaks stdio works the same way: the command is npx -y cosine-astro-mcp.

Tools

All tools are read-only and deterministic for a given input (except where a date defaults to "now").

Birth data

natalchart, annualprofection, and the natal / persona / personb objects of transits and synastry take:

Shortened. The full README is on GitHub.

Nothing above is checked by us. What we check is on the safety report.

Cosine Astro: common questions

Is Cosine Astro MCP server safe?: Yes, by our scan: it is graded A (89/100). Read the Cosine Astro safety report
How do I install Cosine Astro?: It runs on your machine. Copy the Claude Code, Cursor, VS Code or Claude Desktop config from the install section.
Does Cosine Astro need an API key?: Not as far as the registry entry and our scan can tell: no credentials are declared or required.
Is Cosine Astro maintained?: The last commit was 18 days ago (2026-10-17). The latest release is v0.1.0.
How does Cosine Astro compare with other MCP servers?: safety score 89/100 (higher than 80% of 48,255 servers); tools 6 (the typical server has 7); tools that change things 0% (typical: 0%. Fewer write tools means less an agent can break). Full comparison.