AstroMCP

gaia

Read-onlyIdempotent

Queries DR3 sources within a sky radius, returning nearest matches first with photometry, parallax signal-to-noise, proper motion, RUWE, variability, and a likely-star flag.

Instructions

Gaia DR3 sources within radius, nearest first: G, BP-RP, parallax (+S/N), proper motion, RUWE, variability flag, and a 'likely_star' flag (parallax S/N > 3 or PM > 5 mas/yr).

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": {
      "ra": "<ra>",
      "dec": "<dec>"
    },
    "name": "gaia"
  }
}

Input Schema

Name	Required	Description	Default
`ra`	Yes
`dec`	Yes
`radius_arcsec`	No

Output Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

First observedv0.1.0Nov 3, 2026

TDQS

A3.5/5.0

Behavior4/5

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

Annotations already declare read-only, idempotent, open-world behavior, so the description is free to add value — and it does: result ordering (nearest first) and the exact rule behind the derived 'likely_star' flag (parallax S/N > 3 or PM > 5 mas/yr). It does not disclose any cap on the number of rows returned, which is a meaningful omission for a cone search.

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?

One dense, front-loaded sentence with no filler; the core operation comes before the field list. Slightly overloaded by cramming the flag definition into parentheses, but nothing is wasted.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness3/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

An output schema exists, so the column enumeration is arguably redundant, and the real gaps — radius units, coordinate frame, and any result-size limit — go unaddressed. Adequate to call the tool, but not fully self-sufficient for a catalog cone search.

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

Parameters2/5

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

Schema coverage is 0%, so the description carries the full burden. 'Within radius' hints at the third parameter's role, but ra/dec coordinate frame (ICRS, presumably), radius units (arcsec), and the default radius of 5 are never explained, leaving the two required parameters undocumented.

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?

States the resource (Gaia DR3 sources), the operation (cone search within radius), the ordering (nearest first), and enumerates the returned columns. The catalog name alone separates it from catalog siblings like simbad and vsx.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

There is no explicit guidance on when to use this versus simbad, vsx, or ztf_objects_near, and no stated preconditions. Usage must be inferred purely from 'Gaia DR3 sources within radius'.

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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