RoxyAPI Astrology MCP server

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Generate natal chart - Birth chart calculator API with houses and aspects

post_astrology_natal_chart

Read-only

Calculate a complete Western natal chart with tropical zodiac: 14 celestial bodies, 12 house cusps, aspects, Ascendant and Midheaven from any birth date, time and location.

Instructions

Calculate complete Western astrology natal chart (birth chart) with tropical zodiac. Returns all 14 celestial bodies (the 10 classical planets Sun through Pluto, the lunar nodes, Chiron, and Black Moon Lilith), 12 house cusps with customizable house systems (Placidus, Whole Sign, Equal, Koch), major and minor aspects, Ascendant, Midheaven, dominant elements and modalities. Perfect for astrology apps, birth chart generators, horoscope websites, and astrological consultation tools. Verified against NASA JPL Horizons.

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 for dividing the chart into 12 houses. Placidus (default) is most popular in Western astrology and time-sensitive. Whole Sign assigns one sign per house (simpler, ancient). Equal houses divide chart into 30° segments from Ascendant. Koch emphasizes houses in high latitudes.	placidus

Output Schema

Name	Required	Description	Default
`houses`	Yes
`vertex`	Yes
`aspects`	Yes
`planets`	Yes
`summary`	Yes
`patterns`	No
`ascendant`	Yes
`midheaven`	Yes
`houseSystem`	Yes
`birthDetails`	Yes
`partOfFortune`	Yes
`aspectsInterpretation`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedv1.1.2Oct 5, 2026

changedInput schema / examples

Previous value: -[
-  {
-    "date": "1990-07-15",
-    "latitude": 40.7128,
-    "longitude": -74.006,
-    "time": "14:30:00",
-    "timezone": -5
-  }
-]New value: +[
+  {
+    "date": "1990-07-15",
+    "latitude": 40.7128,
+    "longitude": -74.006,
+    "time": "14:30:00",
+    "timezone": "America/New_York"
+  }
+]

changedInput schema / properties / timezone / example

Previous value: --5New value: +"America/New_York"

First observedv0.1.0Oct 4, 2026

TDQS

A3.7/5.0

Behavior3/5

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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds that the calculation uses the tropical zodiac and is 'Verified against NASA JPL Horizons,' which is a useful accuracy signal, but it does not disclose rate limits, authentication needs, or other operational behavior; much of the remaining text restates return contents that the output schema covers.

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 first sentence is front-loaded with the core purpose and return contents, and the final accuracy claim is useful. The middle marketing sentence ('Perfect for...') does not help an agent invoke the tool and could be removed, but overall the description is appropriately sized.

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?

For a 9-parameter, read-only calculation tool with full schema coverage, an output schema, and safety annotations, the description provides enough context about scope and outputs. It does not need to explain return values because an output schema exists, though it could better route agents among the many sibling chart tools.

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 all nine parameters—including the house system enum and node type—are already fully documented in the input schema. The description mentions customizable house systems but adds no syntax, defaults, or constraints beyond what the schema provides.

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?

States a specific verb ('Calculate') and resource ('Western astrology natal chart'), and enumerates the returned bodies, houses, aspects, Ascendant, Midheaven, and dominants. This distinguishes it from narrower sibling tools like post_astrology_planets or post_astrology_houses, which each return a subset.

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 says it is 'Perfect for astrology apps, birth chart generators, horoscope websites, and astrological consultation tools,' which implies usage context but never states when to choose this complete-chart tool over siblings like post_astrology_planets or post_astrology_aspects. No exclusions or prerequisites are given.

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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