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Perigee

by io.github.dlamarre-dev
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Sunlight and shadow

perigee_shadow
Read-only

Whether an object is in sunlight, in the penumbra or in the umbra of the body it orbits (Earth satellites: the Earth's shadow; lunar and Martian orbiters: the Moon's or Mars'), and when it next enters and leaves the shadow (default: over two orbits, at most 12 hours). Explains why a satellite crossing the night sky suddenly fades out.

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": {
      "id": "<id>"
    },
    "name": "perigee_shadow"
  }
}

Input Schema

NameRequiredDescriptionDefault
idYesObject id from perigee_find (NORAD number, mission id, planet, "moon:<id>", "site:<id>", "launch:<id>", "star:<id>", "comet:<id>", "asteroid:<id>" or a dwarf planet name), e.g. "25544" for the ISS.
dateNoISO 8601 UTC instant, e.g. 2026-12-01T00:00:00Z (default: now).
langNoLanguage of names and texts (default en).
hoursNoLength of the search in hours (default: two orbits).
centreNoBody casting the shadow (default: the one the object orbits).
time_zoneNoIANA time zone for local times, e.g. "Europe/Paris".

Schema Changelog

Changes observed during successful MCP inspections.

  1. First observed

TDQS

A3.8/5.0
Behavior4/5

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

Annotations already mark the tool read-only and open-world; the description adds physical-state definitions and the default two-orbit/12-hour lookahead, plus the fade-out explanation. It does not cover return formatting or edge cases, but with annotations the bar is lower.

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?

Two sentences, front-loaded with the operation and followed by a useful illustrative scenario. Dense but no redundant filler.

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 identifies the returned information (shadow state and next entry/exit times) and the default time span. It stops short of describing the exact return shape or edge cases, but it is sufficient for an agent to call the tool correctly.

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 clarifies the default central body by orbit type and restates the default/maximum search window, but most parameter meaning is already in the schema.

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 states the specific computation: shadow state (sunlight, penumbra, umbra) and next entry/exit times, with the central body clarified for Earth, lunar, and Martian cases. It does not explicitly differentiate this from sibling tools such as perigee_passes or perigee_sky, so it falls short of a 5.

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?

It gives a clear scenario (explaining why a satellite fades out) and default search window, but does not state when to choose this over sibling tools or any exclusions. Usage is implied by the purpose rather than explicitly routed.

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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