Totally Tarot Calculators

Check which planets are retrograde, and until when

check_retrogrades

Read-onlyIdempotent

Reports which planets are retrograde on a date and the two stations that open and close each body's current period ("since 2026-02-14, until 2026-03-07"). Per body: retrograde flag, ecliptic longitude, longitude speed, sign and degree, and both stations with exact UTC instants.

The dates shift every cycle and follow no fixed calendar rule; Mercury stations retrograde three or four times a year. A station is where longitude speed crosses zero, found by bisection for eight bodies, so this takes longer than a single-instant position.

Excluded: the Sun and Moon, which cannot station, and Rahu and Ketu, whose mean motion is backwards throughout. The "excluded" array lists them.

Results include an attribution line and a permalink.

Input Schema

Name	Required	Description	Default
`date`	No	The date, ISO YYYY-MM-DD, 1700-2200. Example: "2026-03-01". Defaults to today (UTC).
`time`	No	Time of day HH:MM, read as UTC. Example: "12:00". Matters within a day of a station.

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedOct 26, 2026

changedInput schema / properties / date / description

Previous value: -"The date, ISO YYYY-MM-DD, 1700-2200. Example: \"2026-03-01\". Omit: today (UTC)."New value: +"The date, ISO YYYY-MM-DD, 1700-2200. Example: \"2026-03-01\". Defaults to today (UTC)."

changedInput schema / properties / time / description

Previous value: -"Time of day HH:MM in UTC, not local and not a birth time. Example: \"12:00\". Matters within a day of a station."New value: +"Time of day HH:MM, read as UTC. Example: \"12:00\". Matters within a day of a station."

Changed2 schema fields changedOct 26, 2026

changedInput schema / properties / date / description

Previous value: -"The date, ISO YYYY-MM-DD, 1700-2200. Example: \"2026-03-01\". The stations returned bracket this date."New value: +"The date, ISO YYYY-MM-DD, 1700-2200. Example: \"2026-03-01\". Omit: today (UTC)."

removedInput schema / required
```
Removed value: -[
-  "date"
-]
```

Changed3 schema fields changedSep 23, 2026

changedInput schema / properties / date / description

Previous value: -"The date, ISO YYYY-MM-DD, zero-padded, between 1700 and 2200. Examples: \"2026-03-01\", today's date for \"is Mercury retrograde right now\". The stations returned bracket the period this date falls inside."New value: +"The date, ISO YYYY-MM-DD, 1700-2200. Example: \"2026-03-01\". The stations returned bracket this date."

changedInput schema / properties / time / description

Previous value: -"Time of day as HH:MM in UTC — not a local time and not a birth time. Example: \"12:00\". Omit it for 00:00 UTC. It only changes the answer within about a day of a station, which is exactly when somebody is likely to be asking."New value: +"Time of day HH:MM in UTC, not local and not a birth time. Example: \"12:00\". Matters within a day of a station."

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": {
-        "bodies": {
-          "items": {
-            "properties": {
-              "currentPeriodEnd": {
-                "description": "The station that closes it. Same shape, same null rule.",
-                "type": "object"
-              },
-              "currentPeriodStart": {
-                "description": "The station that OPENED the period this body is currently in — its type, its exact UTC instant, and the degree it stationed at. null when no station falls inside the search window, which the page says rather than leaving blank. This field and the next are the reason to call this endpoint instead of reading a speed.",
-                "type": "object"
-              },
-              "formattedDegree": {
-                "description": "Degree within the sign, for display.",
-                "type": "string"
-              },
-              "longitudeSpeedPerDay": {
-                "description": "Degrees of ecliptic longitude per day. Negative while retrograde; near zero at a station.",
-                "type": "number"
-              },
-              "planet": {
-                "description": "One of the eight bodies that can station.",
-                "type": "string"
-              },
-              "retrograde": {
-                "description": "Apparent motion at that instant.",
-                "type": "boolean"
-              }
-            },
-            "type": "object"
-          },
-          "type": "array"
-        },
-        "date": {
-          "description": "The date asked about.",
-          "type": "string"
-        },
-        "directNow": {
-          "description": "The bodies moving direct at that instant.",
-          "type": "array"
-        },
-        "excluded": {
-          "items": {
-            "properties": {
-              "bodies": {
-                "description": "What is deliberately not in the list: the Sun and Moon, which cannot station, and Rahu and Ketu, which move backwards every day of their existence.",
-                "type": "array"
-              },
-              "reason": {
-                "description": "Why, in full. Quote it if the user asks about any of those four rather than reporting an absence.",
-                "type": "string"
-              }
-            },
-            "type": "object"
-          },
-          "type": "array"
-        },
-        "instantUTC": {
-          "description": "The instant the speeds were read at. It matters within about a day of a station.",
-          "type": "string"
-        },
-        "retrogradeNow": {
-          "description": "The names only, for a caller that wants the one-line answer. Empty when nothing is retrograde, which is itself the answer.",
-          "type": "array"
-        }
-      },
-      "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

Changed1 schema field changedSep 21, 2026

addedOutput schema / properties / result / properties

Added value: +{
+  "bodies": {
+    "items": {
+      "properties": {
+        "currentPeriodEnd": {
+          "description": "The station that closes it. Same shape, same null rule.",
+          "type": "object"
+        },
+        "currentPeriodStart": {
+          "description": "The station that OPENED the period this body is currently in — its type, its exact UTC instant, and the degree it stationed at. null when no station falls inside the search window, which the page says rather than leaving blank. This field and the next are the reason to call this endpoint instead of reading a speed.",
+          "type": "object"
+        },
+        "formattedDegree": {
+          "description": "Degree within the sign, for display.",
+          "type": "string"
+        },
+        "longitudeSpeedPerDay": {
+          "description": "Degrees of ecliptic longitude per day. Negative while retrograde; near zero at a station.",
+          "type": "number"
+        },
+        "planet": {
+          "description": "One of the eight bodies that can station.",
+          "type": "string"
+        },
+        "retrograde": {
+          "description": "Apparent motion at that instant.",
+          "type": "boolean"
+        }
+      },
+      "type": "object"
+    },
+    "type": "array"
+  },
+  "date": {
+    "description": "The date asked about.",
+    "type": "string"
+  },
+  "directNow": {
+    "description": "The bodies moving direct at that instant.",
+    "type": "array"
+  },
+  "excluded": {
+    "items": {
+      "properties": {
+        "bodies": {
+          "description": "What is deliberately not in the list: the Sun and Moon, which cannot station, and Rahu and Ketu, which move backwards every day of their existence.",
+          "type": "array"
+        },
+        "reason": {
+          "description": "Why, in full. Quote it if the user asks about any of those four rather than reporting an absence.",
+          "type": "string"
+        }
+      },
+      "type": "object"
+    },
+    "type": "array"
+  },
+  "instantUTC": {
+    "description": "The instant the speeds were read at. It matters within about a day of a station.",
+    "type": "string"
+  },
+  "retrogradeNow": {
+    "description": "The names only, for a caller that wants the one-line answer. Empty when nothing is retrograde, which is itself the answer.",
+    "type": "array"
+  }
+}

First observedSep 21, 2026

TDQS

A4.3/5.0

Behavior5/5

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

Annotations already declare read-only, idempotent and closed-world, and the description goes well beyond them: it discloses the computation method (zero-crossing of longitude speed found by bisection for eight bodies), warns that it is slower than a single-instant position call, and enumerates what the response contains including attribution and permalink. Auth, cost and output shape questions are all pre-empted.

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

Conciseness5/5

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

Three short paragraphs, front-loaded with the return contents, then the cost/model note, then exclusions and metadata. Every sentence carries information an agent needs; nothing is padding.

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?

No output schema exists, yet the description enumerates the per-body fields (retrograde flag, longitude, speed, sign, degree, both stations in UTC) plus the excluded array and attribution/permalink. Combined with annotations, 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%, so date format, range and default are already fully documented, and the description's note that time matters within a day of a station largely restates the schema. The one value-add, that station dates shift each cycle with no fixed calendar rule, explains why results vary rather than adding parameter syntax.

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 (reports which planets are retrograde) plus the distinctive extra scope: the two stations opening and closing each body's current period. That is enough to tell it apart from get_planetary_positions and compute_transits 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 Guidelines3/5

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

There is clear scoping guidance — the Sun/Moon and Rahu/Ketu are excluded and surfaced in an 'excluded' array — plus a note that time matters within a day of a station and that the date defaults to today. However, no sibling is named as an alternative, so the agent must infer that get_planetary_positions is the right tool when only plain positions are wanted.

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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