Kerykeion MCP Server

An MCP (Model Context Protocol) server for astrological chart generation using the Kerykeion library. Compatible with Claude Desktop and ChatGPT Desktop.

Features

• Natal Charts - Birth chart generation with planetary positions, aspects, and house placements

• Synastry Charts - Relationship compatibility analysis between two people

• Transit Charts - Current transits to natal positions

• Composite Charts - Midpoint composite for relationship dynamics

• Planetary Returns - Solar, Lunar, and other planetary return charts (with relocation support)

• Event Charts - Charts for specific moments (electional, horary)

• Current Positions - Quick lookup of current planetary positions

• Aspects - Structured natal and synastry aspect lists for AI analysis

• Chart Patterns - Stelliums, T-squares, grand trines/crosses, yods, kites, and element/mode balance, each with a neutral, growth-oriented note

Output Formats

• Text - AI-readable descriptions optimized for LLM interpretation

• SVG - Vector chart images saved to files (path returned in response)

• PNG - High-resolution (1600px) raster images (requires cairosvg)

Related MCP server: auseklis

Astrological Foundations

• Zodiac: Tropical by default. Sidereal is supported on every chart tool via zodiac_type="Sidereal", but requires an explicit sidereal_mode (e.g. "LAHIRI", the standard ayanamsha for Vedic/Jyotish work) -- the server will reject a sidereal request with no mode rather than silently picking one.

• House system: Placidus ("P") by default. Other systems (Whole Sign "W", Koch "K", Equal "A", Campanus "C", Regiomontanus "R", Morinus "M", Porphyry "O", Gauquelin Sectors "G") are available via house_system.

• Interpretation text: the text field in every response is Kerykeion's structured to_context output -- positions, aspects, and dignities. It is not a synthesized reading; synthesis happens in the consuming LLM, guided by the server's interpretation-framing instructions (developmental framing, no fatalistic/medical predictions, birth-time-confidence caveats for house-dependent claims).

• Relationship score: generate_synastry_chart's relationship_score uses Ciro Discepolo's method -- a count of specific aspect contacts, not a holistic verdict on relationship viability.

• Validation: meaning-bearing parameters (house system, zodiac type, sidereal mode, chart style) are rejected with an educational error if invalid, never silently substituted. Every successful response includes applied_settings, echoing exactly what was computed.

Privacy

• All calculation is local and offline (online=False everywhere) -- birth data never leaves the machine running this server.

• Subject names are logged at DEBUG only; INFO-level logs omit personal data.

• Chart files are written to ~/.kerykeion_charts by default, or a custom directory (see output_dir / KERYKEION_OUTPUT_BASE below).

• The default HTTP bind is loopback-only (127.0.0.1); binding to all interfaces requires an explicit opt-in and logs a warning.

Installation

Requirements

• Python 3.10+

• Kerykeion 5.6+ (Swiss Ephemeris via pyswisseph), pytz, cairosvg -- all installed automatically below.

Using uv (Recommended)

cd kerykeion-mcp
uv sync

Using pip

pip install -e .

System Dependencies for PNG Support

For PNG conversion, you need Cairo graphics library:

# Ubuntu/Debian
sudo apt install libcairo2-dev

# macOS
brew install cairo

# Windows - See cairosvg documentation

Development

uv sync --extra dev
uv run pytest -q

Usage

Development Mode (MCP Inspector)

uv run mcp dev src/kerykeion_mcp/server.py

The MCP Inspector opens its own local UI (typically http://localhost:6274) -- it does not serve at :8000/mcp.

Claude Desktop Configuration

Add to your Claude Desktop config file:

macOS: ~/Library/Application Support/Claude/claude_desktop_config.json
Windows: %APPDATA%\Claude\claude_desktop_config.json
Linux: ~/.config/Claude/claude_desktop_config.json

{
  "mcpServers": {
    "kerykeion-charts": {
      "command": "uv",
      "args": [
        "run",
        "--directory", "/path/to/kerykeion-mcp",
        "python", "-m", "kerykeion_mcp.server"
      ]
    }
  }
}

Or install directly:

uv run mcp install src/kerykeion_mcp/server.py --name "Kerykeion Charts"

ChatGPT Desktop Configuration

Important: ChatGPT requires HTTPS URLs for MCP connectors. You'll need to tunnel your local server.

1. Start the server with Streamable HTTP transport:

   uv run python -m kerykeion_mcp.server --http

   Server runs at http://127.0.0.1:8000 by default. Pass --host 0.0.0.0 to bind on all interfaces if you need the tunnel to reach it -- this exposes the server (which accepts birth data and writes files) to your local network, so only do it on a trusted network.

2. Create an HTTPS tunnel using ngrok (or similar):

   ngrok http 8000

   You'll get a URL like: https://abc123.ngrok-free.app

3. Add to ChatGPT:

   • Enable Developer Mode: Settings → Connectors → Advanced → Developer mode

   • Add MCP Server URL: https://abc123.ngrok-free.app

--sse (legacy HTTP+SSE transport) is still available for older clients but is deprecated in favor of --http.

Available Tools

Common Parameters

Most chart tools accept:

• lat/lng: Coordinates (positive N/E, negative S/W)

• tz_str: IANA timezone (e.g., "Europe/Rome", "America/New_York")

• city/nation: Optional labels for the chart header (calculation always uses lat/lng; if omitted, a coordinate-derived label like "41.90N, 12.50E" is used instead of defaulting to Greenwich)

• theme: "classic", "light", "dark", "strawberry", "dark-high-contrast"

• language: "EN" (default), "IT", "FR", "ES", "PT", "CN", "RU", "TR", "DE", "HI"

• house_system: "P" (Placidus), "W" (Whole Sign), "K" (Koch), "M" (Morinus), etc.

• zodiac_type / sidereal_mode: "Tropical" (default) or "Sidereal" (requires sidereal_mode, e.g. "LAHIRI")

• output_format: "text", "images", or "all"

• output_dir: Custom directory to save chart images (optional; must resolve under ~/.kerykeion_charts or KERYKEION_OUTPUT_BASE)

• chart_style: "full" (default), "wheel_only", or "aspect_grid"

generate_planetary_return additionally accepts return_month/return_day (defaults to today, so lunar returns aren't stuck searching from January), return_lat/return_lng/return_tz_str to cast the return chart for the person's current location instead of their birth location, and return_city/return_nation to label that location (relocated returns default to a coordinate label). Sidereal return charts are rejected with an explanatory error — see Roadmap.

generate_synastry_chart returns relationship_score as an object (value, description, is_destiny_sign, breakdown, scale, note) using Ciro Discepolo's method — one lens among many, not a verdict on relationship viability.

get_chart_patterns returns patterns (a list of {type, planets, note} -- plus apex/trine_planets for T-squares/kites), and element_balance/mode_balance as {counts, missing}, e.g.:

{
  "patterns": [
    {"type": "grand_trine", "planets": ["Jupiter", "Moon", "Venus"], "note": "an easeful circuit of talent that rewards conscious activation rather than passive reliance"}
  ],
  "element_balance": {"counts": {"Fire": 2, "Earth": 3, "Air": 4, "Water": 1}, "missing": []},
  "mode_balance": {"counts": {"Cardinal": 3, "Fixed": 4, "Mutable": 3}, "missing": []}
}

Response Format

Every tool returns status ("success" or "error") and, on success, applied_settings reporting exactly what was computed:

{
  "status": "success",
  "chart_type": "Natal",
  "subject_name": "Test",
  "applied_settings": {
    "house_system": "P (Placidus)",
    "zodiac_type": "Tropical",
    "sidereal_mode": null,
    "theme": "classic",
    "language": "EN",
    "chart_style": "full"
  },
  "text": "AI-readable chart analysis...",
  "svg_path": "/home/user/.kerykeion_charts/natal_test_20260106.svg",
  "png_path": "/home/user/.kerykeion_charts/natal_test_20260106.png",
  "output_dir": "/home/user/.kerykeion_charts"
}

Invalid input returns a structured error instead of a raw exception:

{
  "status": "error",
  "error": "Longitude 500.0 is outside the valid range -180 to +180 (positive = East).",
  "hint": ""
}

Note: Chart images are saved to files rather than returned inline. This keeps responses small and prevents MCP clients from showing "Tool result too large" messages. The AI assistant can read SVG files directly from svg_path if needed for embedding.

Embedding Charts in Claude Artifacts

Method 1: Read SVG File (Recommended)

The AI assistant can read the SVG file directly from svg_path and embed its contents in an HTML artifact.

Method 2: PNG with File Path

Response includes png_path for local file linking:

![Chart](file:///C:/Users/.../chart.png)

Download the markdown file - image renders from local path.

Example Usage

Ask Claude or ChatGPT:

"Generate a natal chart for someone born June 15, 1990 at 2:30 PM in Rome (lat: 41.9028, lng: 12.4964, timezone: Europe/Rome)"

"Create a synastry chart comparing Person A (born Jan 1, 1985 in NYC) and Person B (born Dec 25, 1987 in London)"

"What are the current planetary transits to my natal chart?"

Prompts

The server includes pre-defined prompts to guide conversations:

• natal_chart_prompt - Template for creating natal charts

• synastry_prompt - Template for relationship compatibility

• transit_prompt - Template for transit analysis

Roadmap

• Unknown-birth-time support — noon default with suppressed angles/houses, so house-dependent claims are never presented for an unknown time.

• Annual profections tool — time-lord technique that pairs naturally with the existing return charts.

• Solar-arc directions — a widely used predictive technique not covered by transits or returns.

• Sidereal return charts — blocked upstream: kerykeion's return search matches the natal sidereal longitude against transiting tropical longitudes (verified by probe, ~25 days off for LAHIRI), so the server rejects sidereal returns rather than shipping silently wrong charts.

• Transit-aspect list tool — deliberately deferred; the Immanuel MCP's transit_to_natal tools already cover fast transit aspect analysis in this stack.

License

MIT