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Western Astrology MCP Server by RoxyAPI

Composite Chart - Midpoint relationship chart with interpretations

post_astrology_composite_chart
Read-only

Generate a composite chart by calculating midpoints between two natal charts. The composite chart represents the relationship as a single entity, showing its core identity, emotional bond, communication style, and growth direction. Uses the midpoint method: planets, angles and house cusps are each the midpoint of the two natal values, so the Ascendant always sits on the first cusp. Returns composite planetary positions, house cusps, Ascendant, Midheaven, aspects, and relationship interpretation. Composite chart API, midpoint chart calculator, relationship astrology, couple chart analysis.

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.
person1YesFirst person birth details (date, time, location, timezone).
person2YesSecond person birth details (date, time, location, timezone).
houseSystemNoHouse system for the composite chart. Placidus (default), Whole Sign, Equal, or Koch.placidus

Output Schema

TableJSON Schema
NameRequiredDescriptionDefault
aspectsYes
person1Yes
person2Yes
interpretationYes
compositeHousesYes
compositePlanetsYes
compositeAscendantYes
compositeMidheavenYes

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": {
      +    "aspects": {
      +      "items": {
      +        "properties": {
      +          "angle": {
      +            "type": "number"
      +          },
      +          "interpretation": {
      +            "enum": [
      +              "harmonious",
      +              "challenging",
      +              "neutral"
      +            ],
      +            "type": "string"
      +          },
      +          "isApplying": {
      +            "type": "boolean"
      +          },
      +          "orb": {
      +            "type": "number"
      +          },
      +          "planet1": {
      +            "enum": [
      +              "Sun",
      +              "Moon",
      +              "Mercury",
      +              "Venus",
      +              "Mars",
      +              "Jupiter",
      +              "Saturn",
      +              "Uranus",
      +              "Neptune",
      +              "Pluto",
      +              "North Node",
      +              "South Node",
      +              "Chiron",
      +              "Black Moon Lilith"
      +            ],
      +            "type": "string"
      +          },
      +          "planet2": {
      +            "enum": [
      +              "Sun",
      +              "Moon",
      +              "Mercury",
      +              "Venus",
      +              "Mars",
      +              "Jupiter",
      +              "Saturn",
      +              "Uranus",
      +              "Neptune",
      +              "Pluto",
      +              "North Node",
      +              "South Node",
      +              "Chiron",
      +              "Black Moon Lilith"
      +            ],
      +            "type": "string"
      +          },
      +          "strength": {
      +            "maximum": 100,
      +            "minimum": 0,
      +            "type": "number"
      +          },
      +          "type": {
      +            "enum": [
      +              "CONJUNCTION",
      +              "OPPOSITION",
      +              "TRINE",
      +              "SQUARE",
      +              "SEXTILE",
      +              "SEMI_SEXTILE",
      +              "QUINCUNX",
      +              "SEMI_SQUARE",
      +              "SESQUIQUADRATE"
      +            ],
      +            "type": "string"
      +          }
      +        },
      +        "required": [
      +          "planet1",
      +          "planet2",
      +          "type",
      +          "angle",
      +          "orb",
      +          "isApplying",
      +          "strength",
      +          "interpretation"
      +        ],
      +        "type": "object"
      +      },
      +      "type": "array"
      +    },
      +    "compositeAscendant": {
      +      "properties": {
      +        "degree": {
      +          "type": "number"
      +        },
      +        "longitude": {
      +          "type": "number"
      +        },
      +        "sign": {
      +          "type": "string"
      +        }
      +      },
      +      "required": [
      +        "sign",
      +        "degree",
      +        "longitude"
      +      ],
      +      "type": "object"
      +    },
      +    "compositeHouses": {
      +      "items": {
      +        "properties": {
      +          "degree": {
      +            "type": "number"
      +          },
      +          "longitude": {
      +            "type": "number"
      +          },
      +          "number": {
      +            "type": "number"
      +          },
      +          "sign": {
      +            "type": "string"
      +          }
      +        },
      +        "required": [
      +          "number",
      +          "sign",
      +          "degree",
      +          "longitude"
      +        ],
      +        "type": "object"
      +      },
      +      "type": "array"
      +    },
      +    "compositeMidheaven": {
      +      "properties": {
      +        "degree": {
      +          "type": "number"
      +        },
      +        "longitude": {
      +          "type": "number"
      +        },
      +        "sign": {
      +          "type": "string"
      +        }
      +      },
      +      "required": [
      +        "sign",
      +        "degree",
      +        "longitude"
      +      ],
      +      "type": "object"
      +    },
      +    "compositePlanets": {
      +      "items": {
      +        "properties": {
      +          "compositeInterpretation": {
      +            "properties": {
      +              "keywords": {
      +                "items": {
      +                  "type": "string"
      +                },
      +                "type": "array"
      +              },
      +              "relationshipMeaning": {
      +                "type": "string"
      +              },
      +              "summary": {
      +                "type": "string"
      +              }
      +            },
      +            "required": [
      +              "summary",
      +              "relationshipMeaning",
      +              "keywords"
      +            ],
      +            "type": "object"
      +          },
      +          "degree": {
      +            "maximum": 30,
      +            "minimum": 0,
      +            "type": "number"
      +          },
      +          "house": {
      +            "maximum": 12,
      +            "minimum": 1,
      +            "type": "integer"
      +          },
      +          "isRetrograde": {
      +            "type": "boolean"
      +          },
      +          "latitude": {
      +            "type": "number"
      +          },
      +          "longitude": {
      +            "maximum": 360,
      +            "minimum": 0,
      +            "type": "number"
      +          },
      +          "name": {
      +            "enum": [
      +              "Sun",
      +              "Moon",
      +              "Mercury",
      +              "Venus",
      +              "Mars",
      +              "Jupiter",
      +              "Saturn",
      +              "Uranus",
      +              "Neptune",
      +              "Pluto",
      +              "North Node",
      +              "South Node",
      +              "Chiron",
      +              "Black Moon Lilith"
      +            ],
      +            "type": "string"
      +          },
      +          "sign": {
      +            "type": "string"
      +          },
      +          "speed": {
      +            "type": "number"
      +          }
      +        },
      +        "required": [
      +          "name",
      +          "longitude",
      +          "latitude",
      +          "sign",
      +          "degree",
      +          "house",
      +          "speed",
      +          "isRetrograde"
      +        ],
      +        "type": "object"
      +      },
      +      "type": "array"
      +    },
      +    "interpretation": {
      +      "properties": {
      +        "challenges": {
      +          "items": {
      +            "type": "string"
      +          },
      +          "type": "array"
      +        },
      +        "strengths": {
      +          "items": {
      +            "type": "string"
      +          },
      +          "type": "array"
      +        },
      +        "summary": {
      +          "type": "string"
      +        }
      +      },
      +      "required": [
      +        "summary",
      +        "strengths",
      +        "challenges"
      +      ],
      +      "type": "object"
      +    },
      +    "person1": {
      +      "properties": {
      +        "date": {
      +          "format": "date",
      +          "type": "string"
      +        },
      +        "latitude": {
      +          "maximum": 90,
      +          "minimum": -90,
      +          "type": "number"
      +        },
      +        "longitude": {
      +          "maximum": 180,
      +          "minimum": -180,
      +          "type": "number"
      +        },
      +        "time": {
      +          "format": "time",
      +          "type": "string"
      +        },
      +        "timezone": {
      +          "maximum": 14,
      +          "minimum": -12,
      +          "type": "number"
      +        }
      +      },
      +      "required": [
      +        "date",
      +        "time",
      +        "latitude",
      +        "longitude",
      +        "timezone"
      +      ],
      +      "type": "object"
      +    },
      +    "person2": {
      +      "properties": {
      +        "date": {
      +          "format": "date",
      +          "type": "string"
      +        },
      +        "latitude": {
      +          "maximum": 90,
      +          "minimum": -90,
      +          "type": "number"
      +        },
      +        "longitude": {
      +          "maximum": 180,
      +          "minimum": -180,
      +          "type": "number"
      +        },
      +        "time": {
      +          "format": "time",
      +          "type": "string"
      +        },
      +        "timezone": {
      +          "maximum": 14,
      +          "minimum": -12,
      +          "type": "number"
      +        }
      +      },
      +      "required": [
      +        "date",
      +        "time",
      +        "latitude",
      +        "longitude",
      +        "timezone"
      +      ],
      +      "type": "object"
      +    }
      +  },
      +  "required": [
      +    "person1",
      +    "person2",
      +    "compositePlanets",
      +    "compositeHouses",
      +    "compositeAscendant",
      +    "compositeMidheaven",
      +    "aspects",
      +    "interpretation"
      +  ],
      +  "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

A3.6/5.0
Behavior4/5

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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the safety profile is covered. The description adds useful behavioral context beyond that: it explains the midpoint calculation, the invariant that the Ascendant sits on the first cusp, and exactly what the response contains. 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.

Conciseness3/5

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

The main action and method are front-loaded in the first sentence, and the body is reasonably tight. However, the trailing keyword string — 'Composite chart API, midpoint chart calculator, relationship astrology, couple chart analysis' — is redundant SEO filler that does not help an agent select or invoke the tool.

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 read-only calculation with a full output schema, 100% parameter coverage, and helpful annotations, the description covers what the tool does, how it calculates, and what it returns. The only notable gap is the missing guidance on when to choose this over synastry, but that is a usage-guidance concern already scored separately.

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 schema thoroughly documents all five parameters including person1/person2, lang, compact, and houseSystem. The description adds no parameter-level detail beyond referring to 'two natal charts,' which maps directly to person1/person2. Baseline 3 is appropriate.

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 opens with a specific verb and resource: 'Generate a composite chart by calculating midpoints between two natal charts.' It explains what the chart represents and the method used, which distinguishes it conceptually from relationship-comparison tools like synastry, though it does not explicitly name any sibling tool.

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 implies the tool is for relationship/couple analysis through phrases like 'relationship as a single entity' and 'couple chart analysis,' but it gives no explicit when-to-use guidance, no exclusions, and does not mention alternatives such as post_astrology_synastry. The usage context is clear only by inference.

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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