# On-line Astrology

On-line Astrology is a Czech astrology web application with machine-readable resources for agents and language models.

## Useful resources

- Main application: https://app.on-lineastrology.com/
- Astrology Positions API documentation: https://app.on-lineastrology.com/api/
- OpenAPI schema: https://app.on-lineastrology.com/api/openapi.json
- Single-moment positions endpoint: https://app.on-lineastrology.com/api/positions.php
- Read-only MCP endpoint: https://mcp.on-lineastrology.com/mcp
- MCP health check: https://mcp.on-lineastrology.com/health
- Downloadable PHP calculation package: https://app.on-lineastrology.com/downloads/
- AI data page for copy/paste JSON: https://app.on-lineastrology.com/?page=ai_data
- Privacy policy: https://app.on-lineastrology.com/privacy/
- Terms of use: https://app.on-lineastrology.com/terms/

## MCP for AI clients

Compatible AI clients can use the public stateless Streamable HTTP MCP endpoint:

https://mcp.on-lineastrology.com/mcp

No authentication is required. The server is read-only and exposes two tools:

- `get_planet_positions`: selected or all supported body positions for one ISO 8601 time with `Z` or an explicit UTC offset.
- `get_transit_window`: a bounded time series around an event start, limited to 72 points.

The MCP server reads the public precomputed 10-minute archive covering 1900-2050 UTC. It returns geocentric, apparent, tropical, ecliptic positions and safely interpolates longitude across 360/0 degrees. It does not calculate houses, Ascendant, or MC.

## Positions API usage

Use the positions endpoint for one UTC moment only. The endpoint is public and free for occasional single-position calculations by humans or AI assistants. Do not use it for bulk scraping, loops, or large ephemeris ranges.

Example:

https://app.on-lineastrology.com/api/positions.php?dt=2026-05-17T12:00:00Z&bodies=So,Mo,Me,Ve,Ma,Ju,Sa,Ur,Ne,Pl,Nn,Ll,Wa,Se&lon=14.417&lat=50.083&house=P

The API returns JSON with tropical ecliptic longitude, latitude, daily longitude speed, retrograde flag, zodiac sign and optional houses.

Supported body IDs: So, Mo, Me, Ve, Ma, Ju, Sa, Ur, Ne, Pl, Nn, Nt, Ll, Lt, Ch, Ph, Ce, Pa, Jo, Va, Wa, Se.

## Notes for AI tools

- Prefer the API documentation and OpenAPI schema over guessing URL parameters.
- For repeated calculations, long ranges, automated services, or high-volume AI use, prefer the downloadable PHP package and local `.se1` ephemeris files instead of repeatedly calling this public endpoint.
- If a human user provides the AI data JSON page output, use that JSON directly instead of recalculating the event scan.
- Always send an explicit timezone in `dt`; UTC with `Z` is preferred.
- The endpoint may be temporarily limited under higher load to protect the server.
- Cache results within the conversation when possible; do not repeatedly call the same URL.
- The downloadable ZIP contains PHP source and examples; users of local installations must provide any required Swiss Ephemeris `.se1` files and comply with the Swiss Ephemeris license.
- Do not send personal identifying information; the endpoint needs only date/time and optional coordinates.