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openephemeris

Open Ephemeris

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Python
Remote

ephemeris_solar_return

Read-onlyIdempotent

Calculate the exact Solar Return date and time when the Sun returns to its natal longitude, then generate the Solar Return chart for the year ahead. Get precise annual astrological guidance.

Instructions

Calculate the exact Solar Return date/time — when the Sun returns to its natal ecliptic longitude (happens once per year near the birthday). Returns the Solar Return chart for the year ahead.

CREDIT COST: 5 credits per call.

TARGET DATE: Provide target_datetime near the desired birthday year. If omitted, defaults to the current year's solar return.

EXAMPLE: Solar return for someone born 1985-06-21 (current year): birth_datetime='1985-06-21T14:00:00Z'

EXAMPLE: Solar return for 2027 specifically: birth_datetime='1985-06-21T14:00:00Z', target_datetime='2027-01-01T00:00:00Z'

Input Schema

TableJSON Schema
NameRequiredDescriptionDefault
timezoneNoIANA timezone (e.g. `America/Chicago`); required when the datetime is naive, ignored otherwise.
visual_configNoOptional rendering preferences (only used when include_visual=true).
birth_datetimeYesISO 8601 datetime; zone required — a `Z`/±HH:MM suffix or the `timezone` argument. Date-only resolves to 12:00 UTC. Full rule: server `instructions`.
birth_latitudeNoBirth latitude in decimal degrees (optional, for location context).
include_visualNoWhen true, renders the solar return chart wheel as an SVG and embeds it in the response. The chart image will display in the conversation alongside the data. Costs 2 additional credits on top of the base call cost.
birth_longitudeNoBirth longitude in decimal degrees (optional, for location context).
return_latitudeNoLocation latitude for the return chart (optional, if different from birth location).
target_datetimeNoDate/time near which to find the Solar Return (ISO 8601 with offset or Z). Defaults to approximately 1 year from now if omitted.
return_longitudeNoLocation longitude for the return chart (optional).

Schema Changelog

Changes observed during successful MCP inspections. Dates show when Glama detected each change.

  1. Changed2 schema fields changedv4.8.0
    • changedInput schema / properties / birth_datetime / description
      Previous value: -"ISO 8601 birth date/time. Include offset or Z (e.g. '1985-06-21T14:00:00-05:00')."New value: +"ISO 8601 datetime; zone required — a `Z`/±HH:MM suffix or the `timezone` argument. Date-only resolves to 12:00 UTC. Full rule: server `instructions`."
    • addedInput schema / properties / timezone
      Added value: +{
+  "description": "IANA timezone (e.g. `America/Chicago`); required when the datetime is naive, ignored otherwise.",
+  "type": "string"
+}
  2. First observedv0.1.0

TDQS

A4.4/5.0
Behavior4/5

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint, and the description adds valuable operational context: credit cost per call, additional visual rendering cost, default behavior when target_datetime is omitted, and example usage. No contradiction exists.

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?

The description is front-loaded with the core function, then credit cost, target date guidance, and examples. Every sentence contributes value, and there is no filler or redundancy.

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?

With no output schema, the description does not enumerate return fields but states the high-level result: the Solar Return chart for the year ahead. Given the thorough parameter schema and annotations, this is sufficient for a complex 9-parameter tool, though a bit more return-structure detail could improve completeness.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters4/5

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 meaning through target_datetime guidance and concrete examples showing how to specify current-year versus specific-year returns, which is above baseline.

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?

The description clearly states the tool calculates the exact Solar Return date/time and returns the Solar Return chart. It distinguishes itself from sibling ephemeris tools by specifying the unique event: the Sun returning to its natal ecliptic longitude once per year near the birthday.

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?

The description gives clear usage context: use this tool when you need an annual Solar Return chart, with target_datetime to specify the desired year. It doesn't explicitly name alternatives or exclusions, but the provided examples and target-date guidance make the intended use clear.

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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