AstroWay Astrology API (full catalogue)

Composite Chart

astroway_relational_composite

Read-onlyIdempotent

Calculate a midpoint composite chart: each body at the short-arc midpoint of its two positions, houses derived from the midpoint of the two ARMCs at the mean latitude (not cusp by cusp). When a body sits exactly 180 degrees apart in the two charts its midpoint is ambiguous and the arithmetic mean is returned.

[Group: Comparisons] [Endpoint: POST /v1/composite] [Required: chart1, chart2] [Cost: 50 credits (Tier 3)]

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "chart1": "<chart1>",
      "chart2": "<chart2>"
    },
    "name": "astroway_relational_composite"
  }
}

Input Schema

Name	Required	Description
`chart1`	Yes	Birth data for a single natal chart. Required: date (YYYY-MM-DD), time (HH:mm:ss), latitude and longitude in decimal degrees. The short forms lat, lon, lng and tz are rejected with 400 INVALID_FIELD; pass the full names. timezoneOffset is hours from UTC and defaults to 0, meaning UTC; send timezone instead (an IANA name such as Europe/Kyiv, or auto) and the offset for that date is worked out, summer time included. city is a display label only: nothing here geocodes it, so it never stands in for coordinates. houseSystem is a single house-system letter, P by default; a name such as "Placidus" is refused, and the case matters because I and i are two different Sunshine systems.
`chart2`	Yes	Birth data for a single natal chart. Required: date (YYYY-MM-DD), time (HH:mm:ss), latitude and longitude in decimal degrees. The short forms lat, lon, lng and tz are rejected with 400 INVALID_FIELD; pass the full names. timezoneOffset is hours from UTC and defaults to 0, meaning UTC; send timezone instead (an IANA name such as Europe/Kyiv, or auto) and the offset for that date is worked out, summer time included. city is a display label only: nothing here geocodes it, so it never stands in for coordinates. houseSystem is a single house-system letter, P by default; a name such as "Placidus" is refused, and the case matters because I and i are two different Sunshine systems.
`fields`	No	Compact mode: comma-separated dotted paths to keep, relative to `data`, e.g. "planets.name,planets.longitude,houses.cusp". Omit for the whole response.
`precision`	No	Compact mode: round fractional numbers to this many decimals. Longitudes carry 14 by default; 2 is finer than any chart is drawn.

Output Schema

Name	Required	Description	Default
`input`	No
`houses`	No
`aspects`	No
`planets`	No
`antiscia`	No
`julianDay`	No
`siderealTime`	No
`antisciaAspects`	No
`parallelAspects`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed15 schema fields changedNov 7, 2026

removedInput schema / properties / chart1 / properties / ayanamsaId / anyOf

Removed value: -[
-  {
-    "type": "number"
-  },
-  {
-    "type": "null"
-  }
-]

addedInput schema / properties / chart1 / properties / ayanamsaId / type
```
Added value: +[
+  "number",
+  "null"
+]
```

removedInput schema / properties / chart2 / properties / ayanamsaId / anyOf

Removed value: -[
-  {
-    "type": "number"
-  },
-  {
-    "type": "null"
-  }
-]

addedInput schema / properties / chart2 / properties / ayanamsaId / type
```
Added value: +[
+  "number",
+  "null"
+]
```

changedOutput schema / properties / antiscia / anyOf

Previous value: -[
-  {
-    "items": {
-      "anyOf": [
-        {
-          "additionalProperties": {},
-          "properties": {
-            "antiscion": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "contraAntiscion": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "planetId": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "planetName": {
-              "anyOf": [
-                {
-                  "type": "string"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            }
-          },
-          "type": "object"
-        },
-        {
-          "type": "null"
-        }
-      ]
-    },
-    "type": "array"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "items": {
+      "anyOf": [
+        {
+          "additionalProperties": {},
+          "properties": {
+            "antiscion": {
+              "type": [
+                "number",
+                "null"
+              ]
+            },
+            "contraAntiscion": {
+              "type": [
+                "number",
+                "null"
+              ]
+            },
+            "planetId": {
+              "type": [
+                "number",
+                "null"
+              ]
+            },
+            "planetName": {
+              "type": [
+                "string",
+                "null"
+              ]
+            }
+          },
+          "type": "object"
+        },
+        {
+          "type": "null"
+        }
+      ]
+    },
+    "type": "array"
+  },
+  {
+    "type": "null"
+  }
+]

changedOutput schema / properties / antisciaAspects / anyOf

Previous value: -[
-  {
-    "items": {
-      "anyOf": [
-        {
-          "additionalProperties": {},
-          "properties": {
-            "orb": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "planet1": {
-              "anyOf": [
-                {
-                  "type": "string"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "planet1Id": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "planet2": {
-              "anyOf": [
-                {
-                  "type": "string"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "planet2Id": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "type": {
-              "anyOf": [
-                {
-                  "type": "string"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            }
-          },
-          "type": "object"
-        },
-        {
-          "type": "null"
-        }
-      ]
-    },
-    "type": "array"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "items": {
+      "anyOf": [
+        {
+          "additionalProperties": {},
+          "properties": {
+            "orb": {
+              "type": [
+                "number",
+                "null"
+              ]
+            },
+            "planet1": {
+              "type": [
+                "string",
+                "null"
+              ]
+            },
+            "planet1Id": {
+              "type": [
+                "number",
+                "null"
+              ]
+            },
+            "planet2": {
+              "type": [
+                "string",
+                "null"
+              ]
+            },
+            "planet2Id": {
+              "type": [
+                "number",
+                "null"
+              ]
+            },
+            "type": {
+              "type": [
+                "string",
+                "null"
+              ]
+            }
+          },
+          "type": "object"
+        },
+        {
+          "type": "null"
+        }
+      ]
+    },
+    "type": "array"
+  },
+  {
+    "type": "null"
+  }
+]

changedOutput schema / properties / aspects / anyOf

Previous value: -[
-  {
-    "items": {
-      "anyOf": [
-        {
-          "additionalProperties": {},
-          "properties": {
-            "exactAngle": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "isApplying": {
-              "anyOf": [
-                {
-                  "type": "boolean"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "orb": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "planet1": {
-              "anyOf": [
-                {
-                  "type": "string"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "planet1Id": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "planet2": {
-              "anyOf": [
-                {
-                  "type": "string"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "planet2Id": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "type": {
-              "anyOf": [
-                {
-                  "additionalProperties": {},
-                  "properties": {
-                    "angle": {
-                      "anyOf": [
-                        {
-                          "type": "number"
-                        },
-                        {
-                          "type": "null"
-                        }
-                      ]
-                    },
-                    "color": {
-                      "anyOf": [
-                        {
-                          "type": "string"
-                        },
-                        {
-                          "type": "null"
-                        }
-                      ]
-                    },
-                    "i18nKey": {
-                      "anyOf": [
-                        {
-                          "type": "string"
-                        },
-                        {
-                          "type": "null"
-                        }
-                      ]
-                    },
-                    "isMajor": {
-                      "anyOf": [
-                        {
-                          "type": "boolean"
-                        },
-                        {
-                          "type": "null"
-                        }
-                      ]
-                    },
-                    "name": {
-                      "anyOf": [
-                        {
-                          "type": "string"
-                        },
-                        {
-                          "type": "null"
-                        }
-                      ]
-                    },
-                    "orb": {
-                      "anyOf": [
-                        {
-                          "type": "number"
-                        },
-                        {
-                          "type": "null"
-                        }
-                      ]
-                    },
-                    "symbol": {
-                      "anyOf": [
-                        {
-                          "type": "string"
-                        },
-                        {
-                          "type": "null"
-                        }
-                      ]
-                    }
-                  },
-                  "type": "object"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            }
-          },
-          "type": "object"
-        },
-        {
-          "type": "null"
-        }
-      ]
-    },
-    "type": "array"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "items": {
+      "anyOf": [
+        {
+          "additionalProperties": {},
+          "properties": {
+            "exactAngle": {
+              "type": [
+                "number",
+                "null"
+              ]
+            },
+            "isApplying": {
+              "type": [
+                "boolean",
+                "null"
+              ]
+            },
+            "orb": {
+              "type": [
+                "number",
+                "null"
+              ]
+            },
+            "planet1": {
+              "type": [
+                "string",
+                "null"
+              ]
+            },
+            "planet1Id": {
+              "type": [
+                "number",
+                "null"
+              ]
+            },
+            "planet2": {
+              "type": [
+                "string",
+                "null"
+              ]
+            },
+            "planet2Id": {
+              "type": [
+                "number",
+                "null"
+              ]
+            },
+            "type": {
+              "anyOf": [
+                {
+                  "additionalProperties": {},
+                  "properties": {
+                    "angle": {
+                      "type": [
+                        "number",
+                        "null"
+                      ]
+                    },
+                    "color": {
+                      "type": [
+                        "string",
+                        "null"
+                      ]
+                    },
+                    "i18nKey": {
+                      "type": [
+                        "string",
+                        "null"
+                      ]
+                    },
+                    "isMajor": {
+                      "type": [
+                        "boolean",
+                        "null"
+                      ]
+                    },
+                    "name": {
+                      "type": [
+                        "string",
+                        "null"
+                      ]
+                    },
+                    "orb": {
+                      "type": [
+                        "number",
+                        "null"
+                      ]
+                    },
+                    "symbol": {
+                      "type": [
+                        "string",
+                        "null"
+                      ]
+                    }
+                  },
+                  "type": "object"
+                },
+                {
+                  "type": "null"
+                }
+              ]
+            }
+          },
+          "type": "object"
+        },
+        {
+          "type": "null"
+        }
+      ]
+    },
+    "type": "array"
+  },
+  {
+    "type": "null"
+  }
+]

changedOutput schema / properties / houses / anyOf

Previous value: -[
-  {
-    "additionalProperties": {},
-    "properties": {
-      "armc": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ]
-      },
-      "ascendant": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ]
-      },
-      "cusps": {
-        "anyOf": [
-          {
-            "items": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "type": "array"
-          },
-          {
-            "type": "null"
-          }
-        ]
-      },
-      "equatorialAsc": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ]
-      },
-      "mc": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ]
-      },
-      "system": {
-        "anyOf": [
-          {
-            "type": "string"
-          },
-          {
-            "type": "null"
-          }
-        ]
-      },
-      "vertex": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ]
-      }
-    },
-    "type": "object"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "additionalProperties": {},
+    "properties": {
+      "armc": {
+        "type": [
+          "number",
+          "null"
+        ]
+      },
+      "ascendant": {
+        "type": [
+          "number",
+          "null"
+        ]
+      },
+      "cusps": {
+        "anyOf": [
+          {
+            "items": {
+              "type": [
+                "number",
+                "null"
+              ]
+            },
+            "type": "array"
+          },
+          {
+            "type": "null"
+          }
+        ]
+      },
+      "equatorialAsc": {
+        "type": [
+          "number",
+          "null"
+        ]
+      },
+      "mc": {
+        "type": [
+          "number",
+          "null"
+        ]
+      },
+      "system": {
+        "type": [
+          "string",
+          "null"
+        ]
+      },
+      "vertex": {
+        "type": [
+          "number",
+          "null"
+        ]
+      }
+    },
+    "type": "object"
+  },
+  {
+    "type": "null"
+  }
+]

changedOutput schema / properties / input / anyOf

Previous value: -[
-  {
-    "additionalProperties": {},
-    "properties": {
-      "city": {
-        "anyOf": [
-          {
-            "type": "string"
-          },
-          {
-            "type": "null"
-          }
-        ]
-      },
-      "date": {
-        "anyOf": [
-          {
-            "type": "string"
-          },
-          {
-            "type": "null"
-          }
-        ]
-      },
-      "houseSystem": {
-        "anyOf": [
-          {
-            "type": "string"
-          },
-          {
-            "type": "null"
-          }
-        ]
-      },
-      "latitude": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ]
-      },
-      "longitude": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ]
-      },
-      "name": {
-        "anyOf": [
-          {
-            "type": "string"
-          },
-          {
-            "type": "null"
-          }
-        ]
-      },
-      "time": {
-        "anyOf": [
-          {
-            "type": "string"
-          },
-          {
-            "type": "null"
-          }
-        ]
-      },
-      "timezoneOffset": {
-        "anyOf": [
-          {
-            "type": "number"
-          },
-          {
-            "type": "null"
-          }
-        ]
-      }
-    },
-    "type": "object"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "additionalProperties": {},
+    "properties": {
+      "city": {
+        "type": [
+          "string",
+          "null"
+        ]
+      },
+      "date": {
+        "type": [
+          "string",
+          "null"
+        ]
+      },
+      "houseSystem": {
+        "type": [
+          "string",
+          "null"
+        ]
+      },
+      "latitude": {
+        "type": [
+          "number",
+          "null"
+        ]
+      },
+      "longitude": {
+        "type": [
+          "number",
+          "null"
+        ]
+      },
+      "name": {
+        "type": [
+          "string",
+          "null"
+        ]
+      },
+      "time": {
+        "type": [
+          "string",
+          "null"
+        ]
+      },
+      "timezoneOffset": {
+        "type": [
+          "number",
+          "null"
+        ]
+      }
+    },
+    "type": "object"
+  },
+  {
+    "type": "null"
+  }
+]

removedOutput schema / properties / julianDay / anyOf

Removed value: -[
-  {
-    "type": "number"
-  },
-  {
-    "type": "null"
-  }
-]

addedOutput schema / properties / julianDay / type
```
Added value: +[
+  "number",
+  "null"
+]
```

changedOutput schema / properties / parallelAspects / anyOf

Previous value: -[
-  {
-    "items": {
-      "anyOf": [
-        {
-          "additionalProperties": {},
-          "properties": {
-            "exactDiff": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "orb": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "planet1": {
-              "anyOf": [
-                {
-                  "type": "string"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "planet1Id": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "planet2": {
-              "anyOf": [
-                {
-                  "type": "string"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "planet2Id": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "type": {
-              "anyOf": [
-                {
-                  "type": "string"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            }
-          },
-          "type": "object"
-        },
-        {
-          "type": "null"
-        }
-      ]
-    },
-    "type": "array"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "items": {
+      "anyOf": [
+        {
+          "additionalProperties": {},
+          "properties": {
+            "exactDiff": {
+              "type": [
+                "number",
+                "null"
+              ]
+            },
+            "orb": {
+              "type": [
+                "number",
+                "null"
+              ]
+            },
+            "planet1": {
+              "type": [
+                "string",
+                "null"
+              ]
+            },
+            "planet1Id": {
+              "type": [
+                "number",
+                "null"
+              ]
+            },
+            "planet2": {
+              "type": [
+                "string",
+                "null"
+              ]
+            },
+            "planet2Id": {
+              "type": [
+                "number",
+                "null"
+              ]
+            },
+            "type": {
+              "type": [
+                "string",
+                "null"
+              ]
+            }
+          },
+          "type": "object"
+        },
+        {
+          "type": "null"
+        }
+      ]
+    },
+    "type": "array"
+  },
+  {
+    "type": "null"
+  }
+]

changedOutput schema / properties / planets / anyOf

Previous value: -[
-  {
-    "items": {
-      "anyOf": [
-        {
-          "additionalProperties": {},
-          "properties": {
-            "declination": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "distance": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "id": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "isRetrograde": {
-              "anyOf": [
-                {
-                  "type": "boolean"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "latitude": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "longitude": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "name": {
-              "anyOf": [
-                {
-                  "type": "string"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "rightAscension": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "speedDist": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "speedLat": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            },
-            "speedLong": {
-              "anyOf": [
-                {
-                  "type": "number"
-                },
-                {
-                  "type": "null"
-                }
-              ]
-            }
-          },
-          "type": "object"
-        },
-        {
-          "type": "null"
-        }
-      ]
-    },
-    "type": "array"
-  },
-  {
-    "type": "null"
-  }
-]New value: +[
+  {
+    "items": {
+      "anyOf": [
+        {
+          "additionalProperties": {},
+          "properties": {
+            "declination": {
+              "type": [
+                "number",
+                "null"
+              ]
+            },
+            "distance": {
+              "type": [
+                "number",
+                "null"
+              ]
+            },
+            "id": {
+              "type": [
+                "number",
+                "null"
+              ]
+            },
+            "isRetrograde": {
+              "type": [
+                "boolean",
+                "null"
+              ]
+            },
+            "latitude": {
+              "type": [
+                "number",
+                "null"
+              ]
+            },
+            "longitude": {
+              "type": [
+                "number",
+                "null"
+              ]
+            },
+            "name": {
+              "type": [
+                "string",
+                "null"
+              ]
+            },
+            "rightAscension": {
+              "type": [
+                "number",
+                "null"
+              ]
+            },
+            "speedDist": {
+              "type": [
+                "number",
+                "null"
+              ]
+            },
+            "speedLat": {
+              "type": [
+                "number",
+                "null"
+              ]
+            },
+            "speedLong": {
+              "type": [
+                "number",
+                "null"
+              ]
+            }
+          },
+          "type": "object"
+        },
+        {
+          "type": "null"
+        }
+      ]
+    },
+    "type": "array"
+  },
+  {
+    "type": "null"
+  }
+]

removedOutput schema / properties / siderealTime / anyOf

Removed value: -[
-  {
-    "type": "number"
-  },
-  {
-    "type": "null"
-  }
-]

addedOutput schema / properties / siderealTime / type
```
Added value: +[
+  "number",
+  "null"
+]
```

Changed2 schema fields changedNov 6, 2026

changedInput schema / properties / chart1 / description

Previous value: -"Birth data for a single natal chart. Required: date (YYYY-MM-DD), time (HH:mm:ss), latitude and longitude in decimal degrees. The short forms lat, lon, lng and tz are rejected with 400 INVALID_FIELD; pass the full names. timezoneOffset is hours from UTC and defaults to 0, meaning UTC; send timezone instead (an IANA name such as Europe/Kyiv, or auto) and the offset for that date is worked out, summer time included. city is a display label only: nothing here geocodes it, so it never stands in for coordinates. houseSystem is a single Swiss Ephemeris letter, P by default; a name such as \"Placidus\" is refused, and the case matters because I and i are two different Sunshine systems."New value: +"Birth data for a single natal chart. Required: date (YYYY-MM-DD), time (HH:mm:ss), latitude and longitude in decimal degrees. The short forms lat, lon, lng and tz are rejected with 400 INVALID_FIELD; pass the full names. timezoneOffset is hours from UTC and defaults to 0, meaning UTC; send timezone instead (an IANA name such as Europe/Kyiv, or auto) and the offset for that date is worked out, summer time included. city is a display label only: nothing here geocodes it, so it never stands in for coordinates. houseSystem is a single house-system letter, P by default; a name such as \"Placidus\" is refused, and the case matters because I and i are two different Sunshine systems."

changedInput schema / properties / chart2 / description

Previous value: -"Birth data for a single natal chart. Required: date (YYYY-MM-DD), time (HH:mm:ss), latitude and longitude in decimal degrees. The short forms lat, lon, lng and tz are rejected with 400 INVALID_FIELD; pass the full names. timezoneOffset is hours from UTC and defaults to 0, meaning UTC; send timezone instead (an IANA name such as Europe/Kyiv, or auto) and the offset for that date is worked out, summer time included. city is a display label only: nothing here geocodes it, so it never stands in for coordinates. houseSystem is a single Swiss Ephemeris letter, P by default; a name such as \"Placidus\" is refused, and the case matters because I and i are two different Sunshine systems."New value: +"Birth data for a single natal chart. Required: date (YYYY-MM-DD), time (HH:mm:ss), latitude and longitude in decimal degrees. The short forms lat, lon, lng and tz are rejected with 400 INVALID_FIELD; pass the full names. timezoneOffset is hours from UTC and defaults to 0, meaning UTC; send timezone instead (an IANA name such as Europe/Kyiv, or auto) and the offset for that date is worked out, summer time included. city is a display label only: nothing here geocodes it, so it never stands in for coordinates. houseSystem is a single house-system letter, P by default; a name such as \"Placidus\" is refused, and the case matters because I and i are two different Sunshine systems."

First observedOct 5, 2026

TDQS

A3.6/5.0

Behavior4/5

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

Annotations already cover read-only, idempotent, non-destructive. The description adds genuinely new behavior: the exact algorithm variant used for houses (mean ARMC, not cusp-by-cusp), the documented tie-breaking rule when bodies are 180° apart, and the 50-credit Tier 3 cost with the endpoint path. Cost and algorithmic edge-case handling are not derivable from annotations, so this earns above a baseline.

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?

Two sentences of substance front-load the definition and edge case, followed by a compact bracketed metadata block for group, endpoint, required params, and cost. No filler. Slightly dense prose in the first sentence, but every clause carries information.

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

Completeness5/5

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

For a two-chart read-only calculation tool, the description plus a fully documented nested schema and an output schema leave nothing an agent needs to call it correctly. The ambiguous-midpoint rule and the house-derivation caveat cover the main correctness traps, and cost is disclosed.

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%, and the nested chart1/chart2 objects are documented in depth, so the schema does the heavy lifting. The description only repeats '[Required: chart1, chart2]' and adds no syntax or format meaning beyond that. 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?

Names a specific verb and resource ('Calculate a midpoint composite chart') and then defines the technique precisely (short-arc midpoints per body, houses from the mean of the two ARMCs at mean latitude). An agent knows exactly what computation this returns. It stops short of a 5 because it never explicitly distinguishes itself from sibling composite-adjacent tools like astroway_relational_davison or astroway_relational_synastry.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

No statement of when to prefer a composite over Davison, synastry, or coalescent, and no prerequisites or exclusions. The only selection-relevant metadata is the '[Group: Comparisons]' tag and the required-parameter line, which signal context but not decision criteria.

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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