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Western Astrology MCP Server by RoxyAPI

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Black Moon Lilith calculator - mean and true lunar apogee in the natal chart

post_astrology_lilith
Read-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.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
dateYesBirth date in YYYY-MM-DD format. Determines planetary positions for the specific calendar day.
langNoResponse 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
timeYesBirth time in 24-hour HH:MM:SS format. Determines the Ascendant (rising sign) and house cusps. Use 12:00:00 if unknown.
compactNoSet 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.
latitudeYesBirth location latitude in decimal degrees (-90 to 90). Positive = North, negative = South.
nodeTypeNoLunar 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
timezoneYesTimezone: 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.
longitudeYesBirth location longitude in decimal degrees (-180 to 180). Positive = East, negative = West.
houseSystemNoHouse system used to place each Lilith variant in a house. Placidus (default), Whole Sign, Equal, or Koch.placidus

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
lilithYes
summaryYes
houseSystemYes
birthDetailsYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed1 schema field changed
    • changedInput schema / properties / timezone / description
      Previous value: -"Timezone: IANA name (e.g. \"America/New_York\", \"Europe/London\") OR decimal hours from UTC (e.g. -5 for EST, 1 for CET). IANA strings are resolved to the offset in force at the given date and time, so you can pass `cities[0].timezone` from /location/search directly."New value: +"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."
  2. Changed1 schema field changed
    • changedOutput schema / (root)
      Previous value: -nullNew value: +{
+  "properties": {
+    "birthDetails": {
+      "properties": {
+        "date": {
+          "format": "date",
+          "type": "string"
+        },
+        "latitude": {
+          "maximum": 90,
+          "minimum": -90,
+          "type": "number"
+        },
+        "longitude": {
+          "maximum": 180,
+          "minimum": -180,
+          "type": "number"
+        },
+        "time": {
+          "format": "time",
+          "type": "string"
+        },
+        "timezone": {
+          "maximum": 14,
+          "minimum": -12,
+          "type": "number"
+        }
+      },
+      "required": [
+        "date",
+        "time",
+        "latitude",
+        "longitude",
+        "timezone"
+      ],
+      "type": "object"
+    },
+    "houseSystem": {
+      "enum": [
+        "placidus",
+        "whole-sign",
+        "equal",
+        "koch"
+      ],
+      "type": "string"
+    },
+    "lilith": {
+      "items": {
+        "properties": {
+          "degree": {
+            "maximum": 30,
+            "minimum": 0,
+            "type": "number"
+          },
+          "house": {
+            "maximum": 12,
+            "minimum": 1,
+            "type": "integer"
+          },
+          "interpretation": {
+            "type": "string"
+          },
+          "isRetrograde": {
+            "type": "boolean"
+          },
+          "latitude": {
+            "type": "number"
+          },
+          "longitude": {
+            "maximum": 360,
+            "minimum": 0,
+            "type": "number"
+          },
+          "note": {
+            "type": "string"
+          },
+          "sign": {
+            "type": "string"
+          },
+          "speed": {
+            "type": "number"
+          },
+          "variant": {
+            "enum": [
+              "mean",
+              "true"
+            ],
+            "type": "string"
+          },
+          "variantLocalized": {
+            "type": "string"
+          }
+        },
+        "required": [
+          "variant",
+          "longitude",
+          "latitude",
+          "sign",
+          "degree",
+          "house",
+          "speed",
+          "isRetrograde",
+          "interpretation",
+          "note"
+        ],
+        "type": "object"
+      },
+      "type": "array"
+    },
+    "summary": {
+      "type": "string"
+    }
+  },
+  "required": [
+    "birthDetails",
+    "houseSystem",
+    "lilith",
+    "summary"
+  ],
+  "type": "object"
+}
  3. Changed1 schema field changed
    • changedInput schema / properties / timezone / description
      Previous value: -"Timezone: IANA name (e.g. \"America/New_York\", \"Europe/London\") OR decimal hours from UTC (e.g. -5 for EST, 1 for CET). IANA strings are resolved to the DST-correct offset for the given date, so you can pass `cities[0].timezone` from /location/search directly."New value: +"Timezone: IANA name (e.g. \"America/New_York\", \"Europe/London\") OR decimal hours from UTC (e.g. -5 for EST, 1 for CET). IANA strings are resolved to the offset in force at the given date and time, so you can pass `cities[0].timezone` from /location/search directly."
  4. Changed2 schema fields changed
    • changedInput schema / properties / lang / description
      Previous value: -"Response language (ISO 639-1). Supported: en, tr, de, es, hi, pt, fr, ru. Defaults to en. Languages without translations yet return English."New value: +"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."
    • changedInput schema / properties / lang / enum
      Previous value: -[
-  "en",
-  "tr",
-  "de",
-  "es",
-  "hi",
-  "pt",
-  "fr",
-  "ru"
-]New value: +[
+  "en",
+  "tr",
+  "de",
+  "es",
+  "hi",
+  "pt",
+  "fr",
+  "ru",
+  "zh-Hans",
+  "zh-Hant"
+]
  5. Changed3 schema fields changed
    • addedInput schema / examples
      Added value: +[
+  {
+    "date": "1990-07-15",
+    "latitude": 40.7128,
+    "longitude": -74.006,
+    "time": "14:30:00",
+    "timezone": -5
+  }
+]
    • changedInput schema / properties / compact / description
      Previous value: -"Set true to receive the exact same data in a token-optimized shape that is cheaper for you to read: whitespace is stripped and every array of same-shaped objects is encoded columnar as {\"__cols\":[field names],\"__rows\":[[values]]}, so each field name is sent once instead of once per row. Fully lossless (no field or value is dropped or changed) and typically 40 to 52 percent fewer tokens on large results. Prefer true whenever token or inference cost matters. Default false returns standard indented JSON."New value: +"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."
    • changedInput schema / properties / nodeType / description
      Previous value: -"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 what most Western software reports (Astrolabe, Cafe Astrology, TimePassages), which is why it is the default here; astro-seek and the Steven Forrest evolutionary school use mean, so pass \"mean\" to match those. 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\"."New value: +"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\"."
  6. Changed1 schema field changed
    • addedInput schema / properties / nodeType
      Added value: +{
+  "default": "true",
+  "description": "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 what most Western software reports (Astrolabe, Cafe Astrology, TimePassages), which is why it is the default here; astro-seek and the Steven Forrest evolutionary school use mean, so pass \"mean\" to match those. 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\".",
+  "enum": [
+    "mean",
+    "true"
+  ],
+  "example": "true",
+  "type": "string"
+}
  7. Changed1 schema field changed
    • changedInput schema / properties / compact / description
      Previous value: -"Return the same data in a token-optimized compact shape (minified, with same-shaped arrays encoded columnar) to reduce LLM token cost. Lossless: no fields are dropped. Default false."New value: +"Set true to receive the exact same data in a token-optimized shape that is cheaper for you to read: whitespace is stripped and every array of same-shaped objects is encoded columnar as {\"__cols\":[field names],\"__rows\":[[values]]}, so each field name is sent once instead of once per row. Fully lossless (no field or value is dropped or changed) and typically 40 to 52 percent fewer tokens on large results. Prefer true whenever token or inference cost matters. Default false returns standard indented JSON."
  8. Changed1 schema field changed
    • addedInput schema / properties / compact
      Added value: +{
+  "default": false,
+  "description": "Return the same data in a token-optimized compact shape (minified, with same-shaped arrays encoded columnar) to reduce LLM token cost. Lossless: no fields are dropped. Default false.",
+  "type": "boolean"
+}
  9. Changed2 schema fields changed
    • changedInput schema / properties / timezone / anyOf
      Previous value: -[
-  {
-    "maximum": 14,
-    "minimum": -14,
-    "type": "number"
-  },
-  {
-    "pattern": "^[A-Za-z_]+(?:\\/[A-Za-z0-9_+-]+){0,2}$",
-    "type": "string"
-  }
-]New value: +[
+  {
+    "maximum": 14,
+    "minimum": -14,
+    "type": "number"
+  },
+  {
+    "type": "string"
+  }
+]
    • changedInput schema / properties / timezone / description
      Previous value: -"Timezone: decimal hours from UTC (e.g. -5 for EST, 5.5 for IST) OR IANA name (e.g. \"America/New_York\", \"Asia/Kolkata\"). IANA strings are resolved to the DST-correct offset for the given date, so you can pass `cities[0].timezone` from /location/search directly."New value: +"Timezone: IANA name (e.g. \"America/New_York\", \"Europe/London\") OR decimal hours from UTC (e.g. -5 for EST, 1 for CET). IANA strings are resolved to the DST-correct offset for the given date, so you can pass `cities[0].timezone` from /location/search directly."
  10. First observed

TDQS

A4.1/5.0
Behavior4/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

The description adds value beyond annotations: it explains that true Lilith can shift sign and turn retrograde, and discusses the mean/true difference in a way not covered by annotations. It also mentions the return includes interpretation, which is useful. The annotations already declare read-only and non-destructive, and the description aligns with that, so no contradiction.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

The description is two sentences, with the first sentence covering core functionality and variants, and the second describing outputs and audience. It is front-loaded with the core action and returns, but the second sentence adds slightly fluffy language ('wild, suppressed, and reclaimed self') that is not strictly necessary. Overall, it's efficient but not perfectly lean.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

Given the tool's moderate complexity with 9 parameters and an output schema, the description adequately covers inputs, outputs, and use cases. It discusses the mean/true distinction, return fields, and audience. The only minor gap is not explicitly contrasting with very similar sibling tools, but the output schema and detailed param descriptions cover most needs.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Though schema coverage is 100%, the description enhances several parameters: it explains nodeType in depth (mean vs true, sign agreement, cusp proximity), and clarifies timezone resolution for IANA vs numeric offsets. It also implicitly ties latitude/longitude to birth location, though less explicitly for those. This goes beyond the schema's basic field descriptions.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

The description clearly states the tool calculates Black Moon Lilith, specifically both mean and true lunar apogee, for a birth chart. It distinguishes itself from siblings like post_astrology_planets or post_astrology_natal_chart by focusing on this specific point and its variants, making the purpose unambiguous.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines3/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The description implies use for natal astrology apps and agents exploring Lilith's themes, and the distinction between mean and true is explained. However, it doesn't explicitly state when to prefer this over siblings like post_astrology_planets or post_astrology_natal_chart, nor does it mention when not to use it. This is a moderate gap given the large sibling set.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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