RoxyAPI Astrology MCP server

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Solar arc directions calculator - directed chart at one degree per year

post_astrology_solar_arc

Read-only

Calculate a solar arc directed chart from birth to any target date to time major life events, returning each directed point and its interpretation.

Instructions

Calculate a solar arc directed chart for any birth moment and target date. The solar arc is the secondary-progressed Sun longitude minus the natal Sun longitude, about one degree for each year of life, and every natal point including the Ascendant and Midheaven is advanced forward by that same arc. Returns the solar arc, each directed point with its natal and directed longitude, zodiac sign, degree, and a plain language interpretation, for predictive astrology apps timing major life events. Built on accurate tropical chart positions, no astronomy expertise needed.

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: 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.
`targetDate`	Yes	Date to direct the chart to, in YYYY-MM-DD format. Every natal point is advanced by the solar arc accumulated from birth to this date, about one degree for each year of life.

Output Schema

TableJSON Schema

Name	Required	Description	Default
`summary`	Yes
`directed`	Yes
`solarArc`	Yes
`targetDate`	Yes
`birthDetails`	Yes

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Oct 4, 2026

TDQS

A4.2/5.0

Behavior4/5

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

Annotations already declare readOnlyHint=true and destructiveHint=false. The description adds valuable behavioral context: the computation method (solar arc formula), the tropical coordinate basis, and the promise of a plain-language interpretation. It also clarifies the level of user expertise required ('no astronomy expertise needed'). These go beyond the structured metadata.

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

Conciseness5/5

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

Three sentences with no filler. The first sentence immediately states the action and inputs; the second explains the methodology concisely; the third states the outputs and use case. Every sentence earns its place, and the most critical information (what the tool does) is front-loaded.

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 complexity (9 parameters, output schema present, annotations cover safety), the description is nearly complete. It explains the purpose, method, outputs, and intended use case. An output schema exists, so detailed return-value documentation is unnecessary. Minor gaps like house system or handling of unknown birth time are already addressed in the schema.

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 baseline is 3. The description does not add parameter-specific meaning beyond the schema; it only refers to 'birth moment' and 'target date' generically. The schema already fully documents each parameter including formats, defaults, and enumerations, so the description does not need to compensate.

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 a solar arc directed chart for any birth moment and target date.' It clearly distinguishes the tool from siblings by explicitly naming the solar arc technique and explaining its formula (secondary-progressed Sun minus natal Sun). The scope (directed chart with Ascendant and Midheaven) is unambiguous.

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?

Provides clear usage context: 'for predictive astrology apps timing major life events.' It conveys the intended application without explicitly naming alternatives. Since the schema and title already differentiate it from progressions, transits, and other chart tools, the lack of explicit exclusions is acceptable.

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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