RoxyAPI Astrology MCP server

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Calculate house cusps - House system calculator with comparison

post_astrology_houses

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Calculate all 12 astrological house cusps with zodiac signs, degrees, Ascendant, and Midheaven using Placidus, Whole Sign, Equal, or Koch systems. Compare all four side-by-side for chart and educational use.

Instructions

Calculate astrological house cusps using Placidus, Whole Sign, Equal, or Koch house systems. Returns all 12 house cusps with zodiac signs, degrees, Ascendant, and Midheaven. Use "all" parameter to compare all 4 house systems side-by-side. Perfect for astrology charts, house cusp tables, and educational tools showing house system differences. Includes accurate Ascendant and MC calculations.

Input Schema

Name	Required	Description	Default
`date`	Yes	Birth date in YYYY-MM-DD format. Date is critical for house cusp calculations as it determines planetary positions used in some house systems.
`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. Time is ESSENTIAL for accurate house cusps, and even minutes matter. The Ascendant (1st house cusp) changes roughly every 4 minutes. Without accurate time, house placements will be incorrect.
`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). Location determines the local horizon and meridian, which are fundamental to house division. Higher latitudes cause more distortion in time-based systems like Placidus.
`timezone`	Yes	Decimal hours from UTC (e.g. -5 for EST, 5.5 for IST, 9 for JST) OR IANA name (e.g. "America/New_York"). IANA resolved to the DST-correct offset for the chart date.
`longitude`	Yes	Birth location longitude in decimal degrees (-180 to 180). Affects local time and horizon calculations for house cusps.
`houseSystem`	No	House system for dividing ecliptic into 12 houses. Placidus (most popular) uses time, Whole Sign (ancient) uses signs, Equal divides from Ascendant. Use "all" to compare all 4 systems side-by-side for educational purposes.	placidus

Output Schema

Name	Required	Description	Default
`date`	Yes
`time`	Yes
`houses`	Yes
`latitude`	Yes
`timezone`	Yes
`ascendant`	Yes
`longitude`	Yes
`midheaven`	Yes
`comparison`	No
`houseSystem`	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

A3.9/5.0

Behavior3/5

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

Annotations already declare this is a safe read-only, non-destructive operation, so the burden is lightened. The description adds the return scope (12 cusps, signs, degrees, Ascendant, Midheaven) and notes accurate Asc/MC calculations, but the substantive caveat about latitude distortion lives in the schema, not the description.

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?

Front-loaded with the verb and resource, and the 'all' parameter guidance comes before the promotional tail. The closing 'Perfect for astrology charts...' sentence is marketing padding that does not earn its place, mildly diluting an otherwise tight description.

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?

With an output schema covering return values and full schema coverage on inputs, the description only needs to convey purpose, routing, and scope, which it does. It could still help by noting latitude limitations or how it relates to the natal chart sibling, but nothing essential to correct invocation is missing.

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 eight parameters are already documented in the schema, including the houseSystem enum and the 'all' option. The description only restates the house-system choices at a high level, adding no syntax or format detail beyond structured data.

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 and resource ('Calculate astrological house cusps') and enumerates the supported house systems, which distinguishes it from sibling chart tools like post_astrology_natal_chart that also produce houses. An agent can select it without opening the schema.

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?

Gives clear usage context: default single-system calculation, plus the explicit 'all' parameter route for side-by-side comparison, and names target use cases (charts, cusp tables, educational tools). It does not, however, say when a sibling tool such as the natal chart would be preferable, so no exclusions are provided.

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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