Black Moon Lilith calculator - mean and true lunar apogee in the natal chart
post_astrology_lilithRead-only
Calculate Black Moon Lilith for any birth chart, both the mean lunar apogee, the steady and most widely used point, and the true or osculating apogee, the exact position that can shift sign and turn retrograde. Returns the zodiac sign, degree, house, ecliptic longitude and latitude, daily speed, retrograde flag, and a plain language interpretation for each variant. Built for natal astrology apps and AI agents exploring the wild, suppressed, and reclaimed self that Lilith represents.
Example tool call
This call uses example arguments supplied in the tool’s input schema.
{
"id": 1,
"jsonrpc": "2.0",
"method": "tools/call",
"params": {
"arguments": {
"date": "1990-07-15",
"time": "14:30:00",
"latitude": 40.7128,
"timezone": "America/New_York",
"longitude": -74.006
},
"name": "post_astrology_lilith"
}
}Input Schema
| Name | Required | Description | Default |
|---|---|---|---|
| date | Yes | Birth date in YYYY-MM-DD format. Determines planetary positions for the specific calendar day. | |
| lang | No | Response language (BCP 47). Supported: en, tr, de, es, hi, pt, fr, ru, zh-Hans, zh-Hant. Defaults to en. Coverage varies by domain, and a field with no translation in the requested language returns English. | en |
| time | Yes | Birth time in 24-hour HH:MM:SS format. Determines the Ascendant (rising sign) and house cusps. Use 12:00:00 if unknown. | |
| compact | No | Set true for the same data in a compact shape: arrays of same-shaped objects arrive columnar as {"__cols":[names],"__rows":[[values]]}. Lossless, typically 40 to 52 percent fewer tokens. | |
| latitude | Yes | Birth location latitude in decimal degrees (-90 to 90). Positive = North, negative = South. | |
| nodeType | No | Lunar node convention. "mean" is the smoothed average node, which always moves retrograde; "true" is the osculating node, which tracks the real perturbed node, oscillates up to about 1.5 degrees either side of the mean on a 173-day cycle, and can briefly turn direct. Neither is more correct and they almost always fall in the same sign. Applies to the North and South Node. True is the osculating node and the default, because it is what most Western chart software reports; mean is the smoothed node preferred by several evolutionary schools, so pass "mean" to match one. Nothing else in the chart changes, and the two agree on the sign except when the node sits within about 1.8 degrees of a cusp. Defaults to "true". | true |
| timezone | Yes | Timezone: an IANA name (e.g. "America/New_York", "Europe/London", or `cities[0].timezone` from /location/search) or decimal hours from UTC (e.g. -5 for EST, 5.5 for IST). An IANA name is resolved to the offset in force at the given date and time. | |
| longitude | Yes | Birth location longitude in decimal degrees (-180 to 180). Positive = East, negative = West. | |
| houseSystem | No | House system used to place each Lilith variant in a house. Placidus (default), Whole Sign, Equal, or Koch. Above the polar circle, quadrant systems fall back to Whole Sign and the echoed houseSystem reports the system actually used. | placidus |
Output Schema
| Name | Required | Description | Default |
|---|---|---|---|
| lilith | Yes | ||
| summary | Yes | ||
| houseSystem | Yes | ||
| birthDetails | Yes |