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Totally Tarot Calculators

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Cast a natal birth chart

compute_birth_chart
Read-onlyIdempotent

Casts a natal chart: each planet's sign and exact degree in both the tropical (Western) and sidereal (Vedic, Lahiri) zodiacs, the ascendant, the twelve Placidus cusps, the midheaven, retrograde state and the Moon's nakshatra. It covers any chart, rising sign, Moon sign or planet-in-house. Takes a birth date (1800-2200) and a place.

The chart uses the UTC offset in force at that place on that date (East Tennessee kept Central time until 1947), and an hour's error moves the ascendant about 15 degrees, usually into another sign, with the houses following. With "time" left out for an unknown birth time, the ascendant, cusps and houses are withheld, because a stand-in time such as noon gives a wrong ascendant.

Results include an attribution line and a permalink.

Input Schema

NameRequiredDescriptionDefault
tzNoIANA zone or numeric UTC offset hours. Example: "America/Indiana/Indianapolis" or "-5". When absent, resolved for the birth date.
latNoLatitude in decimal degrees as a string. Example: "39.76838". Paired with lon.
lonNoLongitude in decimal degrees as a string. Example: "-86.15804". Paired with lat.
dateYesBirth date, ISO YYYY-MM-DD, 1800-2200. Example: "1977-10-19". Other formats such as "19/10/1977" are refused.
timeNoBirth time HH:MM, 24-hour, local at the birthplace. Example: "23:58". Optional; when it is absent the ascendant and houses are withheld.
placeNoTown or city of birth with region and country. Example: "Indianapolis, Indiana, United States". A bare "Springfield" is refused with candidates.

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed5 schema fields changed
    • changedInput schema / properties / date / description
      Previous value: -"Birth date, ISO YYYY-MM-DD, 1800-2200. Example: \"1977-10-19\". \"19/10/1977\" is refused, not guessed."New value: +"Birth date, ISO YYYY-MM-DD, 1800-2200. Example: \"1977-10-19\". Other formats such as \"19/10/1977\" are refused."
    • changedInput schema / properties / lat / description
      Previous value: -"Latitude in decimal degrees as a string. Example: \"39.76838\". Send with lon."New value: +"Latitude in decimal degrees as a string. Example: \"39.76838\". Paired with lon."
    • changedInput schema / properties / lon / description
      Previous value: -"Longitude in decimal degrees as a string. Example: \"-86.15804\". Send with lat."New value: +"Longitude in decimal degrees as a string. Example: \"-86.15804\". Paired with lat."
    • changedInput schema / properties / time / description
      Previous value: -"Birth time HH:MM, 24-hour, LOCAL at the birthplace. Example: \"23:58\". Leave out if unknown; the ascendant and houses are then withheld."New value: +"Birth time HH:MM, 24-hour, local at the birthplace. Example: \"23:58\". Optional; when it is absent the ascendant and houses are withheld."
    • changedInput schema / properties / tz / description
      Previous value: -"IANA zone or numeric UTC offset hours. Example: \"America/Indiana/Indianapolis\" or \"-5\". Omit: resolved for the BIRTH date."New value: +"IANA zone or numeric UTC offset hours. Example: \"America/Indiana/Indianapolis\" or \"-5\". When absent, resolved for the birth date."
  2. Changed1 schema field changed
    • changedInput schema / properties / time / description
      Previous value: -"Birth time HH:MM, 24-hour, LOCAL at the birthplace. Example: \"23:58\". OMIT if unknown; never send \"12:00\"."New value: +"Birth time HH:MM, 24-hour, LOCAL at the birthplace. Example: \"23:58\". Leave out if unknown; the ascendant and houses are then withheld."
  3. Changed7 schema fields changed
    • changedInput schema / properties / date / description
      Previous value: -"Birth date, ISO YYYY-MM-DD, between 1800-01-01 and 2200-12-31. Zero-padded. Example: \"1977-10-19\". \"1977-10-9\" and \"19/10/1977\" are refused rather than interpreted, because guessing which half is the month is how a chart silently becomes a different chart."New value: +"Birth date, ISO YYYY-MM-DD, 1800-2200. Example: \"1977-10-19\". \"19/10/1977\" is refused, not guessed."
    • changedInput schema / properties / lat / description
      Previous value: -"Latitude in decimal degrees, −90 to 90, as a string. Example: \"39.76838\". Only for a caller who already holds exact coordinates; must be sent together with lon. Half a coordinate pair is refused, never completed from the place name."New value: +"Latitude in decimal degrees as a string. Example: \"39.76838\". Send with lon."
    • changedInput schema / properties / lon / description
      Previous value: -"Longitude in decimal degrees, −180 to 180, as a string. Example: \"-86.15804\". Must be sent together with lat."New value: +"Longitude in decimal degrees as a string. Example: \"-86.15804\". Send with lat."
    • changedInput schema / properties / place / description
      Previous value: -"Town or city of birth, with the region and country when the name is a common one. Examples: \"Indianapolis, Indiana, United States\", \"Reykjavík, Iceland\", \"Varanasi, Uttar Pradesh, India\". A bare \"Springfield\" or \"Cambridge\" is refused with a list of the candidate places rather than resolved to one, because they sit in different time zones and would produce different charts. Not needed if lat and lon are given."New value: +"Town or city of birth with region and country. Example: \"Indianapolis, Indiana, United States\". A bare \"Springfield\" is refused with candidates."
    • changedInput schema / properties / time / description
      Previous value: -"Birth time as HH:MM on a 24-hour clock, in LOCAL time at the birthplace — not UTC. Example: \"23:58\" for two minutes to midnight, \"09:07\" for morning. OMIT THIS FIELD ENTIRELY if the birth time is unknown. Do not send \"12:00\", \"00:00\" or any invented value: the result would carry an ascendant and twelve houses that are a guess, and nothing downstream would mark them as one. Omitted, the answer returns the planetary positions and states plainly that it is withholding the ascendant and the houses."New value: +"Birth time HH:MM, 24-hour, LOCAL at the birthplace. Example: \"23:58\". OMIT if unknown; never send \"12:00\"."
    • changedInput schema / properties / tz / description
      Previous value: -"IANA zone name, or a plain numeric UTC offset in hours. Examples: \"America/Indiana/Indianapolis\", \"-5\", \"5.75\" for Nepal. Leave it out and the zone is resolved for the BIRTH DATE — including historic reassignments — which is almost always what you want. Send it only when the user has told you the offset and it disagrees with the map."New value: +"IANA zone or numeric UTC offset hours. Example: \"America/Indiana/Indianapolis\" or \"-5\". Omit: resolved for the BIRTH date."
    • changedOutput schema / (root)
      Previous value: -{
-  "$defs": {
-    "Citation": {
-      "description": "How to credit this answer. Present on every response, successes and refusals alike.",
-      "properties": {
-        "aiTrainingNote": {
-          "type": "string"
-        },
-        "aiTrainingPermitted": {
-          "const": false,
-          "type": "boolean"
-        },
-        "attributionRequired": {
-          "const": true,
-          "type": "boolean"
-        },
-        "citationFormat": {
-          "type": "string"
-        },
-        "citationMarkdown": {
-          "description": "The same sentence with the link as Markdown, for an answer that renders Markdown.",
-          "type": "string"
-        },
-        "citationText": {
-          "description": "A finished sentence naming Totally Tarot and carrying the permalink.",
-          "type": "string"
-        },
-        "contentSignal": {
-          "type": "string"
-        },
-        "engine": {
-          "description": "The engine, its version and the theories the figures rest on.",
-          "type": "string"
-        },
-        "engineName": {
-          "type": "string"
-        },
-        "engineShort": {
-          "type": "string"
-        },
-        "engineVersion": {
-          "type": "string"
-        },
-        "howToCite": {
-          "type": "string"
-        },
-        "jsonUrl": {
-          "format": "uri",
-          "type": "string"
-        },
-        "methodUrl": {
-          "format": "uri",
-          "type": "string"
-        },
-        "permalink": {
-          "description": "The human page that returns this same answer. This is the URL to link.",
-          "format": "uri",
-          "type": "string"
-        },
-        "publisher": {
-          "type": "string"
-        },
-        "sourceName": {
-          "type": "string"
-        },
-        "sourceUrl": {
-          "format": "uri",
-          "type": "string"
-        },
-        "termsUrl": {
-          "format": "uri",
-          "type": "string"
-        },
-        "theories": {
-          "items": {
-            "type": "string"
-          },
-          "type": "array"
-        },
-        "usageTerms": {
-          "type": "string"
-        }
-      },
-      "required": [
-        "attributionRequired",
-        "citationText",
-        "permalink",
-        "engine",
-        "termsUrl"
-      ],
-      "type": "object"
-    }
-  },
-  "properties": {
-    "attribution": {
-      "description": "The ready-to-paste credit line. Include this in any answer built on the result.",
-      "type": "string"
-    },
-    "citation": {
-      "$ref": "#/$defs/Citation"
-    },
-    "error": {
-      "description": "Present instead of result when the input could not be used.",
-      "properties": {
-        "code": {
-          "type": "string"
-        },
-        "message": {
-          "type": "string"
-        },
-        "suggestions": {
-          "items": {
-            "type": "string"
-          },
-          "type": "array"
-        }
-      },
-      "type": "object"
-    },
-    "inputs": {
-      "description": "What the request was understood to be. The permalink is built from these.",
-      "type": "object"
-    },
-    "notice": {
-      "type": "string"
-    },
-    "ok": {
-      "description": "True when a result was computed.",
-      "type": "boolean"
-    },
-    "result": {
-      "description": "The computed figures. Absent on a refusal.",
-      "properties": {
-        "omittedBodyNote": {
-          "description": "A sentence when a body we normally place is missing because our source for it does not reach this date. Chiron is the only such body: it comes from a JPL Horizons table covering 1920-01-01 to 2060-01-06, while this calculator accepts 1800 to 2200. Quote it rather than letting a reader conclude the body was placed and was unremarkable.",
-          "type": "object"
-        },
-        "origin": {
-          "properties": {
-            "clockChangeNote": {
-              "description": "A sentence when this wall-clock time occurred twice, or never occurred, because clocks changed that day. Says which of the two instants was used and how far the ascendant moves if the other was meant. Quote it with the offset.",
-              "type": "object"
-            },
-            "dstRuleNote": {
-              "description": "A sentence when a pre-1967 United States summer offset is inherited from the town the zone is named after rather than recorded for the birthplace. Names that town and the standard-time alternative. Quote it with the offset.",
-              "type": "object"
-            },
-            "historicNote": {
-              "description": "A sentence when a historic zone reassignment was applied, null when none was. Worth surfacing: it is the difference between a right and a wrong ascendant.",
-              "type": "object"
-            },
-            "latitude": {
-              "description": "The resolved latitude, never a default.",
-              "type": "number"
-            },
-            "localMeanTimeNote": {
-              "description": "A sentence when standard time had not yet reached this place, so the offset is mean time computed from the birthplace's own meridian. Names the longitude used and how far it is from the one the time zone database would have used. Quote it with the offset.",
-              "type": "object"
-            },
-            "longitude": {
-              "description": "The resolved longitude.",
-              "type": "number"
-            },
-            "offsetLabel": {
-              "description": "That zone's offset at that instant, written out.",
-              "type": "string"
-            },
-            "timezone": {
-              "description": "The IANA zone resolved for the birth DATE, not for today.",
-              "type": "string"
-            },
-            "utcInstant": {
-              "description": "The instant the chart was cast for, in UTC. Everything else follows from it.",
-              "type": "string"
-            }
-          },
-          "type": "object"
-        },
-        "timeKnown": {
-          "description": "false when no birth time was given. The ascendant and houses are then absent rather than guessed.",
-          "type": "boolean"
-        },
-        "vedic": {
-          "properties": {
-            "nakshatra": {
-              "description": "The lunar mansion the Moon occupied AT THE BIRTH INSTANT. A point-in-time fact with no interval attached, which is what makes it different from the panchang tool's nakshatra: that one is the mansion running over a stretch of a given day and carries the instants it begins and ends. A birth chart has no validity window, so this field has no boundaries and should not be quoted as though it did.",
-              "type": "string"
-            },
-            "planets": {
-              "items": {
-                "properties": {
-                  "sign": {
-                    "description": "The same instant read against the sidereal zodiac, Lahiri ayanamsa.",
-                    "type": "string"
-                  }
-                },
-                "type": "object"
-              },
-              "type": "array"
-            }
-          },
-          "type": "object"
-        },
-        "western": {
-          "properties": {
-            "ascendantFormatted": {
-              "description": "The ascendant in degrees and minutes. Absent when the birth time is unknown.",
-              "type": "string"
-            },
-            "houseSystem": {
-              "description": "Which house system produced the cusps. Placidus below about 66.06 degrees of latitude, Porphyry at or above it, where Placidus is undefined. Null when the birth time is unknown. Quote this rather than assuming Placidus.",
-              "type": "string"
-            },
-            "houses": {
-              "description": "Twelve house cusps, in the system named by result.western.houseSystem. Empty when the birth time is unknown.",
-              "type": "array"
-            },
-            "moonSign": {
-              "description": "Tropical moon sign.",
-              "type": "string"
-            },
-            "planets": {
-              "items": {
-                "properties": {
-                  "formattedDegree": {
-                    "description": "Degree within the sign, for display.",
-                    "type": "string"
-                  },
-                  "longitude": {
-                    "description": "Ecliptic longitude in degrees, 0 to 360 — the figure to compute with.",
-                    "type": "number"
-                  },
-                  "name": {
-                    "description": "The body.",
-                    "type": "string"
-                  },
-                  "retrograde": {
-                    "description": "Apparent motion at that instant.",
-                    "type": "boolean"
-                  },
-                  "sign": {
-                    "description": "Its sign.",
-                    "type": "string"
-                  }
-                },
-                "type": "object"
-              },
-              "type": "array"
-            },
-            "sunSign": {
-              "description": "Tropical sun sign.",
-              "type": "string"
-            }
-          },
-          "type": "object"
-        }
-      },
-      "type": "object"
-    },
-    "summary": {
-      "description": "The answer in one sentence.",
-      "type": "string"
-    },
-    "tool": {
-      "description": "The calculator that answered.",
-      "type": "string"
-    },
-    "toolName": {
-      "type": "string"
-    }
-  },
-  "required": [
-    "ok",
-    "tool",
-    "attribution",
-    "citation"
-  ],
-  "type": "object"
-}New value: +null
  4. Changed1 schema field changed
    • addedOutput schema / properties / result / properties
      Added value: +{
+  "omittedBodyNote": {
+    "description": "A sentence when a body we normally place is missing because our source for it does not reach this date. Chiron is the only such body: it comes from a JPL Horizons table covering 1920-01-01 to 2060-01-06, while this calculator accepts 1800 to 2200. Quote it rather than letting a reader conclude the body was placed and was unremarkable.",
+    "type": "object"
+  },
+  "origin": {
+    "properties": {
+      "clockChangeNote": {
+        "description": "A sentence when this wall-clock time occurred twice, or never occurred, because clocks changed that day. Says which of the two instants was used and how far the ascendant moves if the other was meant. Quote it with the offset.",
+        "type": "object"
+      },
+      "dstRuleNote": {
+        "description": "A sentence when a pre-1967 United States summer offset is inherited from the town the zone is named after rather than recorded for the birthplace. Names that town and the standard-time alternative. Quote it with the offset.",
+        "type": "object"
+      },
+      "historicNote": {
+        "description": "A sentence when a historic zone reassignment was applied, null when none was. Worth surfacing: it is the difference between a right and a wrong ascendant.",
+        "type": "object"
+      },
+      "latitude": {
+        "description": "The resolved latitude, never a default.",
+        "type": "number"
+      },
+      "localMeanTimeNote": {
+        "description": "A sentence when standard time had not yet reached this place, so the offset is mean time computed from the birthplace's own meridian. Names the longitude used and how far it is from the one the time zone database would have used. Quote it with the offset.",
+        "type": "object"
+      },
+      "longitude": {
+        "description": "The resolved longitude.",
+        "type": "number"
+      },
+      "offsetLabel": {
+        "description": "That zone's offset at that instant, written out.",
+        "type": "string"
+      },
+      "timezone": {
+        "description": "The IANA zone resolved for the birth DATE, not for today.",
+        "type": "string"
+      },
+      "utcInstant": {
+        "description": "The instant the chart was cast for, in UTC. Everything else follows from it.",
+        "type": "string"
+      }
+    },
+    "type": "object"
+  },
+  "timeKnown": {
+    "description": "false when no birth time was given. The ascendant and houses are then absent rather than guessed.",
+    "type": "boolean"
+  },
+  "vedic": {
+    "properties": {
+      "nakshatra": {
+        "description": "The lunar mansion the Moon occupied AT THE BIRTH INSTANT. A point-in-time fact with no interval attached, which is what makes it different from the panchang tool's nakshatra: that one is the mansion running over a stretch of a given day and carries the instants it begins and ends. A birth chart has no validity window, so this field has no boundaries and should not be quoted as though it did.",
+        "type": "string"
+      },
+      "planets": {
+        "items": {
+          "properties": {
+            "sign": {
+              "description": "The same instant read against the sidereal zodiac, Lahiri ayanamsa.",
+              "type": "string"
+            }
+          },
+          "type": "object"
+        },
+        "type": "array"
+      }
+    },
+    "type": "object"
+  },
+  "western": {
+    "properties": {
+      "ascendantFormatted": {
+        "description": "The ascendant in degrees and minutes. Absent when the birth time is unknown.",
+        "type": "string"
+      },
+      "houseSystem": {
+        "description": "Which house system produced the cusps. Placidus below about 66.06 degrees of latitude, Porphyry at or above it, where Placidus is undefined. Null when the birth time is unknown. Quote this rather than assuming Placidus.",
+        "type": "string"
+      },
+      "houses": {
+        "description": "Twelve house cusps, in the system named by result.western.houseSystem. Empty when the birth time is unknown.",
+        "type": "array"
+      },
+      "moonSign": {
+        "description": "Tropical moon sign.",
+        "type": "string"
+      },
+      "planets": {
+        "items": {
+          "properties": {
+            "formattedDegree": {
+              "description": "Degree within the sign, for display.",
+              "type": "string"
+            },
+            "longitude": {
+              "description": "Ecliptic longitude in degrees, 0 to 360 — the figure to compute with.",
+              "type": "number"
+            },
+            "name": {
+              "description": "The body.",
+              "type": "string"
+            },
+            "retrograde": {
+              "description": "Apparent motion at that instant.",
+              "type": "boolean"
+            },
+            "sign": {
+              "description": "Its sign.",
+              "type": "string"
+            }
+          },
+          "type": "object"
+        },
+        "type": "array"
+      },
+      "sunSign": {
+        "description": "Tropical sun sign.",
+        "type": "string"
+      }
+    },
+    "type": "object"
+  }
+}
  5. First observed

TDQS

A4.4/5.0
Behavior5/5

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

Annotations already declare read-only, idempotent, non-destructive and closed-world, and the description still adds substantial behavior: historical UTC offset resolution ('East Tennessee kept Central time until 1947'), the ±15° ascendant sensitivity to a one-hour error, and the deliberate degradation when time is omitted (ascendant, cusps and houses withheld rather than substituted with noon). It also notes the attribution line and permalink in results.

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

Conciseness4/5

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

Front-loaded with outputs before caveats, which is the right order. There is some duplication with the schema (the 1800-2200 range and the withheld-houses rule appear in both), costing a bit of tightness.

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?

With no output schema, the description fully enumerates the return payload and adds the attribution/permalink tail. For a six-parameter compute tool it also covers the two ways the call degrades (missing time, ambiguous place) so an agent knows what to expect back.

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 already carries parameter meaning and baseline 3 applies. The description reinforces the time-omission consequence and date range, but largely restates what the schema says ('when it is absent the ascendant and houses are withheld'); it adds no new syntax or format detail.

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

Purpose5/5

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

Specific verb plus resource ('Casts a natal chart') followed by an enumeration of exactly what is returned: planet signs and degrees in two zodiacs, ascendant, twelve Placidus cusps, midheaven, retrograde state, Moon's nakshatra. This is clearly distinguishable from siblings such as get_planetary_positions (current positions) or compute_seven_governors_chart.

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

Usage Guidelines4/5

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

'It covers any chart, rising sign, Moon sign or planet-in-house' tells the agent what question types this tool answers, which is real usage guidance. It stops short of naming an alternative, e.g. when to reach for get_planetary_positions or compute_panchang instead, so there is no explicit exclusion or routing.

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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