Western Astrology MCP Server by RoxyAPI

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

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: 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.
`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.	placidus

TDQS

A4.1/5.0

Behavior4/5

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

Annotations already say readOnly=true and destructive=false; the description adds behavior (true apogee can shift sign and turn retro, mean is steady) and mentions the output fields. This goes beyond the structured hints and helps the agent understand calm, although rate limits and exact limitations are not covered.

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?

Two sentences with the primary result front-loaded; no redundant parameter repetition. The second-half 'wild, suppressed, and reclaimed self' flavor adds context but is slightly decorative rather than operational.

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?

Because there is no output schema, it is valuable—and unusual—that the description names the returned values: sign, degree, house, longitude, latitude, speed, retro flag, and interpretation. Combined with dense input-schema docs, the agent has most of what it needs; the missing piece is a clear mapping between description and nodeType.

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

Parameters3/5

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

Schema description coverage is 100%, so the input schema already does the heavy lifting for all 9 parameters. The description's mean/true discussion supports nodeType conceptually but does not clarify how nodeType maps to the Lilith/apogee variants, and the schema's own nodeType text mentions North/South Nodes, which is slightly confusing.

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 opens with a precise verb and resource: calculate Black Moon Lilith for a birth chart. It also distinguishes the mean vs true lunar apogee and enumerates returned fields (sign, degree, house, speed, retro flag, interpretation). This makes the tool unmistakable among the large sibling set.

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

Usage Guidelines4/5

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

The phrasing 'for any birth chart' and 'Built for natal apps and AI...' gives a clear invocation copn text and target audience. It does not explicitly compare with alternatives like post_astrology_natal_chart, so it stops short of a 5.

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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TDQS

A3.8/5.0

Disambiguation3/5

Most tools are scoped to a clearly distinct domain—moon phases, houses, returns, fixed stars, astrocartography—but several pairs overlap, notably synastry vs. compatibility_score and transits vs. transit_aspects. The descriptions are long and do help an agent choose, but the boundaries are not always obvious at the name level.

Naming Consistency4/5

Every tool follows the same snake_case get_astrology_/post_astrology_ prefix pattern, making the group predictable and readable. However, collection endpoints like get_astrology_planet_meanings_id and get_astrology_signs_id awkwardly combine plural collection and singular id naming, and names like calendar_year_month depart from the cleaner resource+suffix pattern.

Tool Count2/5

With 38 tools, this is well over the 25+ threshold and feels heavy for an agent to traverse. While Western astrology is a broad domain, several near-duplicate endpoints, especially synastry/compatibility and transits/transit_aspects, could be consolidated into fewer, more scoped tools.

Completeness5/5

The toolset is comprehensive, covering natal charts, relationships, transits, returns, progressions, aspects, houses, relocation, and reference data. It includes enough specialized endpoints for both casual horoscope use and in-depth astrological analysis, with no obvious dead ends for the stated domain.

Resources

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