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Western Astrology MCP Server by RoxyAPI

Calculate synastry - Relationship compatibility analysis API

post_astrology_synastry
Read-only

Calculate complete synastry (relationship compatibility) between two natal charts using Western tropical astrology. Analyzes inter-chart aspects between all planets to determine romantic, friendship, and karmic compatibility. Returns compatibility score (0-100), detailed inter-aspects with strength ratings, harmonious vs challenging aspect counts, and relationship dynamics analysis. Perfect for dating apps, matrimonial sites, relationship counseling tools, and astrology compatibility features. Based on professional astrological techniques.

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
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
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.
person1Yes
person2Yes
houseSystemNoHouse system for both natal charts. Placidus (default), Whole Sign, Equal, or Koch.placidus

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
person1Yes
person2Yes
summaryYes
analysisYes
interAspectsYes
compatibilityScoreYes

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed2 schema fields changed
    • changedInput schema / properties / person1 / 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."
    • changedInput schema / properties / person2 / 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": {
      +    "analysis": {
      +      "properties": {
      +        "challenges": {
      +          "items": {
      +            "type": "string"
      +          },
      +          "type": "array"
      +        },
      +        "overall": {
      +          "type": "string"
      +        },
      +        "strengths": {
      +          "items": {
      +            "type": "string"
      +          },
      +          "type": "array"
      +        }
      +      },
      +      "required": [
      +        "overall",
      +        "strengths",
      +        "challenges"
      +      ],
      +      "type": "object"
      +    },
      +    "compatibilityScore": {
      +      "type": "number"
      +    },
      +    "interAspects": {
      +      "items": {
      +        "properties": {
      +          "angle": {
      +            "type": "number"
      +          },
      +          "interpretation": {
      +            "type": "string"
      +          },
      +          "meaning": {
      +            "properties": {
      +              "description": {
      +                "properties": {
      +                  "long": {
      +                    "type": "string"
      +                  },
      +                  "short": {
      +                    "type": "string"
      +                  }
      +                },
      +                "required": [
      +                  "short",
      +                  "long"
      +                ],
      +                "type": "object"
      +              },
      +              "keywords": {
      +                "items": {
      +                  "type": "string"
      +                },
      +                "type": "array"
      +              },
      +              "name": {
      +                "type": "string"
      +              },
      +              "nature": {
      +                "type": "string"
      +              },
      +              "relationshipContext": {
      +                "type": "string"
      +              }
      +            },
      +            "required": [
      +              "name",
      +              "description",
      +              "keywords",
      +              "nature",
      +              "relationshipContext"
      +            ],
      +            "type": "object"
      +          },
      +          "orb": {
      +            "type": "number"
      +          },
      +          "planet1": {
      +            "type": "string"
      +          },
      +          "planet1Localized": {
      +            "type": "string"
      +          },
      +          "planet2": {
      +            "type": "string"
      +          },
      +          "planet2Localized": {
      +            "type": "string"
      +          },
      +          "strength": {
      +            "type": "number"
      +          },
      +          "type": {
      +            "type": "string"
      +          },
      +          "typeLocalized": {
      +            "type": "string"
      +          }
      +        },
      +        "required": [
      +          "planet1",
      +          "planet2",
      +          "type",
      +          "angle",
      +          "orb",
      +          "strength",
      +          "interpretation"
      +        ],
      +        "type": "object"
      +      },
      +      "type": "array"
      +    },
      +    "person1": {
      +      "properties": {
      +        "ascendant": {
      +          "properties": {
      +            "degree": {
      +              "type": "number"
      +            },
      +            "sign": {
      +              "type": "string"
      +            },
      +            "signLocalized": {
      +              "type": "string"
      +            }
      +          },
      +          "required": [
      +            "sign",
      +            "degree"
      +          ],
      +          "type": "object"
      +        },
      +        "moonSign": {
      +          "type": "string"
      +        },
      +        "moonSignLocalized": {
      +          "type": "string"
      +        },
      +        "name": {
      +          "type": "string"
      +        },
      +        "planets": {
      +          "items": {
      +            "properties": {
      +              "degree": {
      +                "type": "number"
      +              },
      +              "house": {
      +                "type": "number"
      +              },
      +              "houseInOtherChart": {
      +                "type": "number"
      +              },
      +              "isRetrograde": {
      +                "type": "boolean"
      +              },
      +              "longitude": {
      +                "type": "number"
      +              },
      +              "name": {
      +                "type": "string"
      +              },
      +              "nameLocalized": {
      +                "type": "string"
      +              },
      +              "sign": {
      +                "type": "string"
      +              },
      +              "signLocalized": {
      +                "type": "string"
      +              }
      +            },
      +            "required": [
      +              "name",
      +              "longitude",
      +              "sign",
      +              "degree",
      +              "house",
      +              "houseInOtherChart",
      +              "isRetrograde"
      +            ],
      +            "type": "object"
      +          },
      +          "type": "array"
      +        },
      +        "sunSign": {
      +          "type": "string"
      +        },
      +        "sunSignLocalized": {
      +          "type": "string"
      +        }
      +      },
      +      "required": [
      +        "ascendant",
      +        "sunSign",
      +        "moonSign",
      +        "planets"
      +      ],
      +      "type": "object"
      +    },
      +    "person2": {
      +      "properties": {
      +        "ascendant": {
      +          "properties": {
      +            "degree": {
      +              "type": "number"
      +            },
      +            "sign": {
      +              "type": "string"
      +            },
      +            "signLocalized": {
      +              "type": "string"
      +            }
      +          },
      +          "required": [
      +            "sign",
      +            "degree"
      +          ],
      +          "type": "object"
      +        },
      +        "moonSign": {
      +          "type": "string"
      +        },
      +        "moonSignLocalized": {
      +          "type": "string"
      +        },
      +        "name": {
      +          "type": "string"
      +        },
      +        "planets": {
      +          "items": {
      +            "properties": {
      +              "degree": {
      +                "type": "number"
      +              },
      +              "house": {
      +                "type": "number"
      +              },
      +              "houseInOtherChart": {
      +                "type": "number"
      +              },
      +              "isRetrograde": {
      +                "type": "boolean"
      +              },
      +              "longitude": {
      +                "type": "number"
      +              },
      +              "name": {
      +                "type": "string"
      +              },
      +              "nameLocalized": {
      +                "type": "string"
      +              },
      +              "sign": {
      +                "type": "string"
      +              },
      +              "signLocalized": {
      +                "type": "string"
      +              }
      +            },
      +            "required": [
      +              "name",
      +              "longitude",
      +              "sign",
      +              "degree",
      +              "house",
      +              "houseInOtherChart",
      +              "isRetrograde"
      +            ],
      +            "type": "object"
      +          },
      +          "type": "array"
      +        },
      +        "sunSign": {
      +          "type": "string"
      +        },
      +        "sunSignLocalized": {
      +          "type": "string"
      +        }
      +      },
      +      "required": [
      +        "ascendant",
      +        "sunSign",
      +        "moonSign",
      +        "planets"
      +      ],
      +      "type": "object"
      +    },
      +    "summary": {
      +      "properties": {
      +        "byType": {
      +          "additionalProperties": {
      +            "type": "number"
      +          },
      +          "type": "object"
      +        },
      +        "challenging": {
      +          "type": "number"
      +        },
      +        "harmonious": {
      +          "type": "number"
      +        },
      +        "neutral": {
      +          "type": "number"
      +        },
      +        "total": {
      +          "type": "number"
      +        }
      +      },
      +      "required": [
      +        "total",
      +        "harmonious",
      +        "challenging",
      +        "neutral",
      +        "byType"
      +      ],
      +      "type": "object"
      +    }
      +  },
      +  "required": [
      +    "person1",
      +    "person2",
      +    "compatibilityScore",
      +    "interAspects",
      +    "summary",
      +    "analysis"
      +  ],
      +  "type": "object"
      +}
  3. Changed2 schema fields changed
    • changedInput schema / properties / person1 / 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."
    • changedInput schema / properties / person2 / 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. Changed4 schema fields changed
    • addedInput schema / examples
      Added value: +[
      +  {
      +    "person1": {
      +      "date": "1990-07-15",
      +      "latitude": 40.7128,
      +      "longitude": -74.006,
      +      "time": "14:30:00",
      +      "timezone": -5
      +    },
      +    "person2": {
      +      "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 / person1 / 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\"."
    • changedInput schema / properties / person2 / 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. Changed2 schema fields changed
    • addedInput schema / properties / person1 / 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"
      +}
    • addedInput schema / properties / person2 / 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. Changed4 schema fields changed
    • changedInput schema / properties / person1 / properties / timezone / anyOf
      Previous value: -[
      -  {
      -    "maximum": 14,
      -    "minimum": -14,
      -    "type": "number"
      -  },
      -  {
      -    "pattern": "^[A-Za-z_]+(?:\\/[A-Za-z0-9_+-]+){0,2}$",
      -    "type": "string"
      -  }
      -]New value: +[
      +  {
      +    "maximum": 14,
      +    "minimum": -14,
      +    "type": "number"
      +  },
      +  {
      +    "type": "string"
      +  }
      +]
    • changedInput schema / properties / person1 / properties / timezone / description
      Previous value: -"Timezone: decimal hours from UTC (e.g. -5 for EST, 5.5 for IST) OR IANA name (e.g. \"America/New_York\", \"Asia/Kolkata\"). IANA strings are resolved to the DST-correct offset for the given date, so you can pass `cities[0].timezone` from /location/search directly."New value: +"Timezone: IANA name (e.g. \"America/New_York\", \"Europe/London\") OR decimal hours from UTC (e.g. -5 for EST, 1 for CET). IANA strings are resolved to the DST-correct offset for the given date, so you can pass `cities[0].timezone` from /location/search directly."
    • changedInput schema / properties / person2 / properties / timezone / anyOf
      Previous value: -[
      -  {
      -    "maximum": 14,
      -    "minimum": -14,
      -    "type": "number"
      -  },
      -  {
      -    "pattern": "^[A-Za-z_]+(?:\\/[A-Za-z0-9_+-]+){0,2}$",
      -    "type": "string"
      -  }
      -]New value: +[
      +  {
      +    "maximum": 14,
      +    "minimum": -14,
      +    "type": "number"
      +  },
      +  {
      +    "type": "string"
      +  }
      +]
    • changedInput schema / properties / person2 / 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

B3.4/5.0
Behavior3/5

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

Annotations already declare readOnlyHint=true and destructiveHint=false, covering the safety profile. The description adds the output shape (compatibility score, inter-aspects with strength ratings, aspect counts, dynamics analysis) and the astrological tradition (Western tropical). It does not disclose edge-case behaviors like fallback for unknown birth times, but the schema addresses that. No contradiction with annotations.

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 four sentences and front-loads the core purpose and method. The use-case sentence earns its place as context, but the closing claim "Based on professional astrological techniques" is filler and adds no functional value.

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

Completeness3/5

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

Given the output schema, annotations, and detailed nested parameter descriptions, the definition is functional. The main gap is the lack of guidance for choosing between this and the closely related compatibility/composite tools, which matters in a large sibling set of astrology endpoints.

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?

Top-level person1 and person2 lack schema descriptions, resulting in 60% coverage; the description's phrase "between two natal charts" helps map those two undocumented parameters to the required inputs. The other parameters (lang, compact, houseSystem) and all nested fields already have detailed schema descriptions, so the description only partially compensates for the coverage gap.

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

Purpose4/5

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

The description states a specific verb ("Calculate"), a concrete resource ("synastry between two natal charts"), and a precise scope ("inter-chart aspects between all planets"). It clearly describes what the tool does, but it does not explicitly distinguish itself from the close sibling post_astrology_compatibility_score, which also handles relationship compatibility.

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 provides implied usage context via concrete use cases ("dating apps, matrimonial sites, relationship counseling tools, and astrology compatibility features"). However, it never names alternatives or states when to prefer this over sibling tools like post_astrology_compatibility_score or post_astrology_composite_chart, so an agent has limited routing guidance.

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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