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openephemeris

Open Ephemeris

by openephemeris
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Python
Remote

Timezone Resolve

timezone_resolve
Read-onlyIdempotent

Resolve coordinates to an IANA timezone and retrieve the historical UTC offset for a given date. Use it to answer location timezone or local birth-time offset questions.

Instructions

Use this when the user asks 'what timezone is this location in' or 'what was the UTC offset there on that date', or coordinates are known and the IANA zone is needed for a local birth time. Returns the IANA zone and, with date, the historical UTC offset. CREDIT COST: 1 credit per call.

Input Schema

NameRequiredDescriptionDefault
dateNoYYYY-MM-DD; adds the UTC offset in force that day. Pre-1970 +1 credit.
latitudeYesDecimal degrees (+N).
longitudeYesDecimal degrees (+E).

Schema Changelog

Changes observed during successful MCP inspections.

  1. Changed3 schema fields changedv4.29.0
    • changedInput schema / properties / date / description
      Previous value: -"Optional birth/event date 'YYYY-MM-DD'. Adds utcOffsetAtDate / utcOffsetMinutes / isDst / tzConfidence. Post-1970 resolves locally (free); pre-1970 consults the API's historical correction overlay (1 extra credit)."New value: +"YYYY-MM-DD; adds the UTC offset in force that day. Pre-1970 +1 credit."
    • changedInput schema / properties / latitude / description
      Previous value: -"Latitude in decimal degrees, -90 to 90 (north positive)."New value: +"Decimal degrees (+N)."
    • changedInput schema / properties / longitude / description
      Previous value: -"Longitude in decimal degrees, -180 to 180 (east positive)."New value: +"Decimal degrees (+E)."
  2. Changed2 schema fields changedv4.24.2
    • addedInput schema / properties / latitude / description
      Added value: +"Latitude in decimal degrees, -90 to 90 (north positive)."
    • addedInput schema / properties / longitude / description
      Added value: +"Longitude in decimal degrees, -180 to 180 (east positive)."
  3. Addedv4.8.0

TDQS

A4.3/5.0
Behavior4/5

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

Annotations already declare readOnlyHint, idempotentHint, and destructiveHint=false. The description adds useful context beyond annotations: credit cost, return content (IANA zone plus historical offset when date is supplied), and the birth-time scenario. It does not discuss rate limits or failure behavior, but it is transparent for a simple lookup.

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 sentences are front-loaded with the trigger condition, then the return behavior and credit cost. There is no redundant or filler language.

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?

For a simple coordinate-to-timezone lookup with complete schema descriptions and rich annotations, the description covers purpose, return values, cost, and date behavior. No output schema exists, but the description states what is returned.

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 all three parameters are already documented. The description reinforces that `date` yields historical UTC offset and that coordinates must be known, but it does not add syntax or edge-case details 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.

Purpose5/5

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

The description states a specific verb and resource: resolving coordinates to an IANA timezone and optionally a historical UTC offset. It gives concrete trigger phrases and clarifies the birth-time use case, making the tool distinguishable from general location_search.

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 explicitly says when to use the tool: user asks about timezone/UTC offset for a location, or coordinates are known and an IANA zone is needed for a local birth time. It does not name an alternative tool or an exclusion case, but the usage context is 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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