Astro Agents - verifiable planetary timing data and astrology

Transits

transits

Read-onlyIdempotent

Western astrology transits: the transits to a natal chart at a moment, and the exact dates transiting aspects perfect over a window of up to a year. 'transit': aspects from the sky at a moment to every natal point, with the natal house each transiting planet occupies. 'window': the exact UTC minute every transiting planet perfects each aspect to each natal point over up to 366 days (62 with the Moon), retrograde passes included. Deterministic (JPL DE440, no LLM); every result carries meta.result_sha256. Price $0.08 per call via REST POST https://astro-agent.dev/v1/western/transits (x402 or MPP); always paid, never a free call.

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": {
      "natal": "<natal>"
    },
    "name": "transits"
  }
}

Input Schema

Name	Required	Description
`natal`	Yes	Birth data.
`window`	No	UTC dates YYYY-MM-DD, at most 366 days apart.
`options`	No	Optional calculation settings; every default is the common Western convention.
`transit`	No	The transit moment. A bare local time is read in the natal place's zone.

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"
-]

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": {
+        "natal": {
+          "description": "The natal chart the transits are measured against: subject, settings, points and angles.",
+          "type": "object"
+        },
+        "settings": {
+          "description": "The aspect set and orbs applied.",
+          "type": "object"
+        },
+        "transit": {
+          "description": "The transit moment: its time, the transiting points and their aspects to the natal chart.",
+          "type": "object"
+        },
+        "warnings": {
+          "description": "Notes on the input or the calculation (for example an assumed noon for an unknown birth time). Present only when there is something to say.",
+          "type": "array"
+        },
+        "window": {
+          "description": "Exact transit hits over the requested window: start, end, whether the Moon is included, precision, count and the list of hits with their exact dates.",
+          "type": "object"
+        }
+      },
+      "required": [
+        "natal",
+        "settings",
+        "transit",
+        "window"
+      ],
+      "type": "object"
+    }
+  },
+  "required": [
+    "endpoint",
+    "result",
+    "meta"
+  ],
+  "type": "object"
+}

Changed7 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')."

addedInput schema / properties / window / properties / end / description

Added value: +"Last UTC date, YYYY-MM-DD, at most 366 days after start."

addedInput schema / properties / window / properties / include_moon / description

Added value: +"Also time the fast Moon transits; the window is then limited to 62 days."

addedInput schema / properties / window / properties / start / description
```
Added value: +"First UTC date, YYYY-MM-DD. Example: '2026-10-01'."
```

First observedOct 3, 2026

TDQS

A3.9/5.0

Behavior5/5

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

Goes well beyond the annotations: discloses determinism (JPL DE440, no LLM), a verifiable meta.result_sha256 (which links to the verify_result_hash sibling), retrograde passes included, and the commercial/auth profile — $0.08 per call via REST POST with x402 or MPP, "always paid, never a free call". The readOnly/idempotent annotations are consistent rather than restated.

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?

Tight and front-loaded: purpose first, then the two modes, then determinism and price. Every sentence carries information, though the REST URL/payment detail could sit in a trailing clause rather than occupying the prime closing position.

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 nested, two-mode tool with an output schema and full annotation coverage, the description covers what an agent needs to call it correctly, including cost and verifiability. The remaining hole is mode arbitration — only 'natal' is required, so nothing states the default or the behavior when both 'transit' and 'window' are omitted.

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 coverage is 100%, so the baseline is 3. The description adds genuine meaning for the 'transit' object (aspects from the sky at a moment to every natal point, plus the natal house of each transiting planet), but the window limits it cites (366 days, 62 with the Moon) merely restate the schema's own parameter descriptions.

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?

The description opens with a specific verb+resource ("Western astrology transits: the transits to a natal chart at a moment") and crisply defines two internal modes, 'transit' vs 'window'. It does not differentiate itself from siblings such as 'aspects', 'sky_today', or 'synastry', which an agent may plausibly confuse with this tool.

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?

"at a moment" vs "exact dates ... over a window of up to a year" implicitly tells the agent which mode to pick, and the 62-day Moon cap is stated. However, it never says which sibling to use instead (e.g. aspects, sky_today, synastry), nor what happens if neither or both of 'transit'/'window' objects are supplied, so mode selection is only implied by the text.

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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