Perigee

Satellite passes over a place

perigee_passes

Read-only

When an Earth satellite (ISS = 25544, Tiangong = 48274, Hubble = 20580, or any NORAD number) passes over a place: rise, highest point and set times with direction (azimuth, compass point) and elevation, and whether it can be seen with the naked eye (sunlit satellite, dark sky) and when. Give the place's latitude and longitude (degrees, east positive) and, for local times, its IANA time zone. Up to 3 days ahead.

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>",
      "latitude": "<latitude>",
      "longitude": "<longitude>"
    },
    "name": "perigee_passes"
  }
}

Input Schema

Name	Required	Description
`id`	Yes	Object 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.
`days`	No	Search length in days (default 3).
`lang`	No	Language of names and texts (default en).
`start`	No	ISO 8601 UTC instant, e.g. 2026-12-01T00:00:00Z (default: now).
`height_m`	No	Observer height above sea level, m.
`latitude`	Yes	Observer latitude, degrees (north positive).
`longitude`	Yes	Observer longitude, degrees (east positive).
`time_zone`	No	IANA time zone for local times, e.g. "America/Toronto".
`min_elevation`	No	Lowest culmination kept and lowest elevation counted as visible, degrees (default 10).

Schema Changelog

Changes observed during successful MCP inspections.

First observedNov 2, 2026

TDQS

A3.7/5.0

Behavior4/5

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

Annotations already establish readOnly and openWorld, so the bar is lower, and the description still adds useful behavior: the 3-day lookahead ceiling and the criteria for naked-eye visibility (sunlit satellite against a dark sky). It stops short of stating defaults or how many passes are returned, but the safety/mutation profile is fully covered by annotations.

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?

The purpose and output content are front-loaded in the first sentence, and the follow-up sentences are short. Some content duplicates the schema (lat/lon sign convention, time zone), so it is not perfectly waste-free.

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 and 9 parameters, the description correctly carries the burden of explaining what comes back (times, directions, elevations, visibility windows) and the time horizon. Defaults such as min_elevation and days are left entirely to the schema, which is acceptable but leaves the visibility threshold under-explained.

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 schema already documents all 9 parameters. The description's note about degrees-east-positive latitude/longitude and the IANA time zone restates what the schema says, and its satellite ID examples (Tiangong 48274, Hubble 20580) only slightly extend the schema's existing ISS example.

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?

Names a specific verb and resource: passes of a named Earth satellite over a given place, and enumerates the return content (rise/culmination/set, azimuth, elevation, naked-eye visibility). It does not name the neighboring tools (perigee_tonight, perigee_sky, perigee_events) that could appear to overlap, so an agent must infer the distinction.

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?

Implies usage ('give the place's latitude and longitude ... for local times, its IANA time zone') and states a horizon limit ('up to 3 days ahead'), which is real guidance. However, there is no explicit when-to-use/when-not framing and no mention of the sibling tools an agent might pick instead for visibility-only or sky-position queries.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

All Perigee tools Inspect

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