Astro Agents - verifiable planetary timing data and astrology

Planetary positions for any date (ephemeris)

planet_positions

Read-onlyIdempotent

Western astrology planet positions and ephemeris API: the zodiac sign, longitude, latitude, speed and retrograde flag of the Sun, Moon, planets, lunar nodes and Lilith at any moment, geocentric or heliocentric, ecliptic or equatorial (declination, out-of-bounds). Geocentric apparent positions from NASA/JPL DE440 for any moment 1800-2200, with sign, degree, element, modality, daily speed and retrograde status. Location is optional (only used to interpret a local time). Options: perspective 'heliocentric' (seen from the Sun) and coordinates 'equatorial' (right ascension, declination, out-of-bounds). Deterministic (JPL DE440, no LLM); every result carries meta.result_sha256. Price $0.01 per call via REST POST https://astro-agent.dev/v1/western/positions (x402 or MPP); each client gets 1 free call on the $0.01-0.02 tools, this one included.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "planet_positions"
  }
}

Input Schema

Name	Required	Description	Default
`date`	No	YYYY-MM-DD (use with 'time' instead of 'datetime').
`time`	No	HH:MM or HH:MM:SS, 24 h. Omit if unknown (computed at 12:00 with a TIME_UNKNOWN warning).
`options`	No	Optional calculation settings; every default is the common Western convention.
`datetime`	No	Local birth date-time, ISO 8601: '1990-05-15T14:30' (local clock time at the place) or with an explicit offset '1990-05-15T14:30:00+02:00'. Alternative: 'date' + 'time'.
`latitude`	No	Decimal degrees, north positive.
`timezone`	No	IANA zone, e.g. 'Asia/Kolkata'. Optional: resolved from the coordinates, with the historical offset (DST, Local Mean Time) of that date.
`longitude`	No	Decimal degrees, east positive.
`time_basis`	No	What the given clock time is: civil wall-clock (default), UTC, Local Mean Time, or true (apparent) solar time.	civil
`ambiguous_time`	No	Which occurrence to use when a local time happens twice (DST fall-back).	earlier

Output Schema

Name	Required	Description
`meta`	No	Provenance of the result.
`error`	No	x402 offer only: why payment is required.
`result`	No	The calculation result.
`accepts`	No	x402 offer only: the payment options (scheme, network, amount, asset, payTo, ...).
`endpoint`	No	The REST route that computed it, e.g. 'western/natal'.
`resource`	No	x402 offer only: the resource being paid for.
`extensions`	No	x402 offer only: protocol extensions (bazaar).
`x402Version`	No	x402 offer only: protocol version (2).

Schema Changelog

Changes observed during successful MCP inspections.

Changed7 schema fields changedNov 3, 2026

addedOutput schema / anyOf

Added value: +[
+  {
+    "required": [
+      "endpoint",
+      "result",
+      "meta"
+    ]
+  },
+  {
+    "required": [
+      "x402Version",
+      "accepts"
+    ]
+  }
+]

addedOutput schema / properties / accepts

Added value: +{
+  "description": "x402 offer only: the payment options (scheme, network, amount, asset, payTo, ...).",
+  "items": {
+    "type": "object"
+  },
+  "minItems": 1,
+  "type": "array"
+}

addedOutput schema / properties / error

Added value: +{
+  "description": "x402 offer only: why payment is required.",
+  "type": "string"
+}

addedOutput schema / properties / extensions

Added value: +{
+  "description": "x402 offer only: protocol extensions (bazaar).",
+  "type": "object"
+}

addedOutput schema / properties / resource

Added value: +{
+  "description": "x402 offer only: the resource being paid for.",
+  "type": "object"
+}

addedOutput schema / properties / x402Version

Added value: +{
+  "description": "x402 offer only: protocol version (2).",
+  "type": "integer"
+}

removedOutput schema / required

Removed value: -[
-  "endpoint",
-  "result",
-  "meta"
-]

Changed2 schema fields changedOct 29, 2026

addedInput schema / properties / options / properties / coordinates

Added value: +{
+  "default": "ecliptic",
+  "description": "'ecliptic' (default: longitude/latitude) or 'equatorial': also each point's right ascension, declination, their daily speeds and an out-of-bounds flag.",
+  "enum": [
+    "ecliptic",
+    "equatorial"
+  ],
+  "type": "string"
+}

addedInput schema / properties / options / properties / perspective

Added value: +{
+  "default": "geocentric",
+  "description": "'geocentric' (default) or 'heliocentric' (geometric, seen from the Sun: Earth instead of Sun and Moon, no lunar points).",
+  "enum": [
+    "geocentric",
+    "heliocentric"
+  ],
+  "type": "string"
+}

Changed1 schema field changedOct 6, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "endpoint": {
+      "description": "The REST route that computed it, e.g. 'western/natal'.",
+      "type": "string"
+    },
+    "meta": {
+      "description": "Provenance of the result.",
+      "properties": {
+        "astronomy_library": {
+          "description": "Astronomy library and version.",
+          "type": "string"
+        },
+        "compute_ms": {
+          "description": "Computation time in milliseconds.",
+          "type": "number"
+        },
+        "computed_at": {
+          "description": "When it was computed (UTC, ISO 8601).",
+          "type": "string"
+        },
+        "deterministic": {
+          "description": "Always true: same input, same result.",
+          "type": "boolean"
+        },
+        "engine": {
+          "description": "Engine name and version.",
+          "type": "string"
+        },
+        "ephemeris": {
+          "description": "Ephemeris used (NASA/JPL DE440).",
+          "type": "string"
+        },
+        "frame": {
+          "description": "Reference frame of the positions.",
+          "type": "string"
+        },
+        "input_sha256": {
+          "description": "SHA-256 of the canonical input.",
+          "type": "string"
+        },
+        "llm_used": {
+          "description": "Always false: no language model is involved.",
+          "type": "boolean"
+        },
+        "payment": {
+          "description": "How this call was paid: protocol ('free' or 'none'), price and the free calls remaining.",
+          "type": "object"
+        },
+        "reproducibility": {
+          "description": "How to reproduce and check this result.",
+          "type": "string"
+        },
+        "result_sha256": {
+          "description": "SHA-256 of the canonical 'result'; check it with verify_result_hash.",
+          "type": "string"
+        }
+      },
+      "required": [
+        "engine",
+        "deterministic",
+        "llm_used",
+        "input_sha256",
+        "result_sha256"
+      ],
+      "type": "object"
+    },
+    "result": {
+      "description": "The calculation result.",
+      "properties": {
+        "points": {
+          "description": "One entry per body or point (Sun to Pluto, lunar nodes, Chiron...): ecliptic longitude, sign, degree in sign, element, modality, latitude, daily speed, retrograde flag, distance in AU and, with a location, the house.",
+          "type": "array"
+        },
+        "settings": {
+          "description": "Settings applied (zodiac).",
+          "type": "object"
+        },
+        "subject": {
+          "description": "The resolved input: 'time' (local input, time zone and historical UTC offset, UT, Julian days, Delta T) and, when given, 'location' (latitude, longitude).",
+          "type": "object"
+        }
+      },
+      "required": [
+        "subject",
+        "settings",
+        "points"
+      ],
+      "type": "object"
+    }
+  },
+  "required": [
+    "endpoint",
+    "result",
+    "meta"
+  ],
+  "type": "object"
+}

Changed4 schema fields changedOct 5, 2026

addedInput schema / properties / options / description

Added value: +"Optional calculation settings; every default is the common Western convention."

addedInput schema / properties / options / properties / house_system / description

Added value: +"House system for cusps and planet houses, e.g. 'placidus' (default) or 'whole_sign'."

addedInput schema / properties / options / properties / luminary_orb_bonus / description

Added value: +"Extra orb in degrees for aspects involving the Sun or the Moon. Example: 2."

addedInput schema / properties / options / properties / zodiac / description

Added value: +"'tropical' (Western, default) or 'sidereal' (pair it with 'ayanamsa')."

First observedOct 3, 2026

TDQS

B3.4/5.0

Behavior3/5

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

Annotations already declare read-only, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds genuinely useful context beyond that: hard date range 1800-2200, deterministic JPL DE440, a per-result meta.result_sha256, and $0.01-per-call payment via x402/MPP with one free call. However, the perspective/coordinates option sentences largely restate schema defaults rather than adding new behavioral detail.

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?

Purpose and coverage are front-loaded, which is good, but the middle repeats itself: the second sentence re-lists sign, degree, speed and retrograde status already named in the first, and the option descriptions duplicate schema enums. Pricing and determinism details earn their place; the rest could be tightened.

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 nine-parameter tool with nested options and an output schema, the description covers scope, date limits, coordinate/perspective modes, defaults philosophy and cost/payment mechanics. The main remaining gap is comparative guidance against the many sibling chart tools, but return values are covered by the output schema.

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 every one of the nine parameters is already documented with defaults, enums and examples. The description adds only the interpretive note that location 'only interprets a local time' and that heliocentric returns Earth instead of Sun/Moon; otherwise it does not go beyond the schema. 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?

States a concrete resource and scope: zodiac sign, longitude, latitude, speed and retrograde flag for Sun, Moon, planets, nodes and Lilith at any moment, geocentric or heliocentric. An agent can tell this is a positional ephemeris rather than a chart or aspect tool, though it never explicitly names siblings like natal_chart or sky_today to sharpen the boundary.

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?

Usage is implied rather than prescribed: 'at any moment 1800-2200' and 'Location is optional (only used to interpret a local time)' tell the agent when coordinates are needed. There is no explicit when-to-use-this-vs-alternative routing, so an agent choosing between this and sky_today or aspects must infer.

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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