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Totally Tarot Calculators

by net.totallytarot
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Convert a date to the Maya calendars

compute_maya_day_sign
Read-onlyIdempotent

Converts a Gregorian date to the Maya calendars: Tzolk'in day sign and tone as written (e.g. "6 Oc"), kin 1-260, the sign's meaning, direction and trecena, the Haab date, the Long Count and the Julian Day Number. It covers a Maya day sign or birth sign, or any event's Maya date.

The method is the Julian Day Number minus a correlation constant, then remainders mod 20, 13, 260 and 365, where an off-by-one gives a real day sign that is the wrong one. Which constant to use is the open argument in Maya calendrics: this uses Goodman-Martinez-Thompson 584283 and returns it. Time of day, place and zone play no part.

Results include an attribution line and a permalink.

Input Schema

NameRequiredDescriptionDefault
dateYesGregorian date to convert, ISO YYYY-MM-DD, year 1-4000, proleptic before 1582. Example: "2012-12-21".

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed2 schema fields changed
    • changedInput schema / properties / date / description
      Previous value: -"The Gregorian date to convert, ISO YYYY-MM-DD, between year 1 and year 4000. Zero-padded, and proleptic Gregorian before 1582. Examples: \"2012-12-21\" (the end of the thirteenth baktun), \"1994-06-05\", \"0790-03-14\". A birth date, today, or a date in the ninth century all work the same way."New value: +"Gregorian date to convert, ISO YYYY-MM-DD, year 1-4000, proleptic before 1582. Example: \"2012-12-21\"."
    • 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": {
-        "daySign": {
-          "properties": {
-            "name": {
-              "description": "The day sign in the conventional spelling.",
-              "type": "string"
-            },
-            "reformedSpelling": {
-              "description": "The same sign in the reformed Guatemalan orthography.",
-              "type": "string"
-            }
-          },
-          "type": "object"
-        },
-        "haab": {
-          "properties": {
-            "written": {
-              "description": "The Haab date, e.g. \"3 Kankin\".",
-              "type": "string"
-            }
-          },
-          "type": "object"
-        },
-        "julianDayNumber": {
-          "description": "The Julian Day Number the conversion went through, so the arithmetic can be checked against any other implementation.",
-          "type": "number"
-        },
-        "kin": {
-          "description": "Position in the 260-day Tzolk'in round, 1 to 260.",
-          "type": "number"
-        },
-        "longCount": {
-          "description": "The Long Count on the GMT correlation constant 584283.",
-          "type": "string"
-        },
-        "tone": {
-          "description": "The tone, 1 to 13.",
-          "type": "number"
-        },
-        "tzolkinDate": {
-          "description": "Tone and sign together, e.g. \"4 Ahau\".",
-          "type": "string"
-        }
-      },
-      "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
  2. Changed1 schema field changed
    • addedOutput schema / properties / result / properties
      Added value: +{
+  "daySign": {
+    "properties": {
+      "name": {
+        "description": "The day sign in the conventional spelling.",
+        "type": "string"
+      },
+      "reformedSpelling": {
+        "description": "The same sign in the reformed Guatemalan orthography.",
+        "type": "string"
+      }
+    },
+    "type": "object"
+  },
+  "haab": {
+    "properties": {
+      "written": {
+        "description": "The Haab date, e.g. \"3 Kankin\".",
+        "type": "string"
+      }
+    },
+    "type": "object"
+  },
+  "julianDayNumber": {
+    "description": "The Julian Day Number the conversion went through, so the arithmetic can be checked against any other implementation.",
+    "type": "number"
+  },
+  "kin": {
+    "description": "Position in the 260-day Tzolk'in round, 1 to 260.",
+    "type": "number"
+  },
+  "longCount": {
+    "description": "The Long Count on the GMT correlation constant 584283.",
+    "type": "string"
+  },
+  "tone": {
+    "description": "The tone, 1 to 13.",
+    "type": "number"
+  },
+  "tzolkinDate": {
+    "description": "Tone and sign together, e.g. \"4 Ahau\".",
+    "type": "string"
+  }
+}
  3. First observed

TDQS

A4.4/5.0
Behavior5/5

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

Annotations only cover the safety profile (read-only, idempotent, closed-world); the description goes well beyond them by disclosing the algorithm, the specific GMT correlation constant 584283 it returns, the off-by-one failure mode that produces a wrong day sign, and the presence of an attribution line and permalink in results. That is exactly the kind of assumption an agent needs to know before trusting or reusing the output.

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 first sentence front-loads the purpose and the full output list; the following paragraphs cover method and result metadata. The middle explanation of remainders and off-by-one is longer than strictly necessary to invoke the tool, but it is cohesive and each part is non-redundant, so the markup is minor.

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?

There is no output schema, and the description compensates fully by enumerating the returned components (Tzolk'in day sign/tone, kin, sign meaning, direction, trecena, Haab, Long Count, Julian Day Number) plus attribution and permalink. Combined with the stated correlation constant, an agent has everything needed to call it and interpret the result.

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 schema already specifies the ISO YYYY-MM-DD pattern, the year 1-4000 range, proleptic handling before 1582, and an example. The description only repeats 'Gregorian date' and adds no format or edge-case detail beyond the schema, so the baseline applies.

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

Purpose5/5

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

States a specific verb and resource ('Converts a Gregorian date to the Maya calendars') and then enumerates the exact outputs (Tzolk'in day sign and tone, kin, Haab, Long Count, JDN). This is clearly distinguishable from siblings like convert_calendar_date or convert_chinese_lunar_date without opening any schema.

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 names the input domain ('a Maya day sign or birth sign, or any event's Maya date') and rules out irrelevant factors ('Time of day, place and zone play no part'), which is a genuine usage boundary. It does not name a sibling alternative for plain Gregorian calendar conversion, so the routing is implied rather than explicit.

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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