mcp-stargazing

get_constellation

Retrieve the altitude and azimuth of a named constellation's center for a specific observer location and time using its name and coordinates.

Instructions

Get the position (altitude/azimuth) of the center of a constellation.

Use when: you need a named constellation's center position at a place and instant. Do not use when: you need to identify which constellation contains arbitrary coordinates, or to choose individual observing targets. Requires: constellation name, observer coordinates, time, and timezone. Follow-up: get_nightly_forecast for individual night targets; plan_stargazing_session for a complete observing decision.

Args: constellation_name: Name of constellation (e.g. "Orion", "Ursa Major") lon: Observer longitude in degrees lat: Observer latitude in degrees time: Observation time string "YYYY-MM-DD HH:MM:SS" time_zone: IANA timezone string

Returns: Dict with keys "data", "_meta". "data" contains name, altitude, azimuth.

Input Schema

Name	Required	Description	Default
`lat`	Yes
`lon`	Yes
`time`	Yes
`time_zone`	Yes
`constellation_name`	Yes

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedv1.0.0Jan 4, 2026

TDQS

A4.3/5.0

Behavior3/5

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

With no annotations, the description carries the full behavioral burden. It states required inputs and return keys, but it does not disclose coordinate frame conventions, altitude/azimuth units, error behavior, or confirm read-only safety beyond the 'Get' verb.

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 and organized into purpose, use/do-not-use, requirements, follow-up, args, and returns. Every sentence serves a clear selection or invocation purpose with no padding.

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?

The description covers the full input set, usage boundaries, and return structure, and an output schema exists. However, it omits some invocation-relevant conventions such as longitude/latitude sign convention and output altitude/azimuth units.

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

Parameters5/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema description coverage is 0%, so the description must compensate and does: it documents all five required parameters, including examples for constellation_name, degrees for lon/lat, the time string format, and IANA timezone. This is substantially more than the schema alone provides.

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: 'Get the position (altitude/azimuth) of the center of a constellation.' It also distinguishes the scope from adjacent needs by noting it is not for identifying which constellation contains arbitrary coordinates or choosing individual observing targets.

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 gives explicit 'Use when' and 'Do not use when' guidance, plus follow-up tools for related observing tasks. The exclusion for identifying a constellation from arbitrary coordinates is clear, but it does not name a specific alternative tool for that case.

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