AstroMCP

ztf_objects_near

Read-onlyIdempotent

Find ZTF (ALeRCE) objects within a specified radius of sky coordinates to check whether a position matches known objects.

Instructions

ZTF objects (ALeRCE) within radius of a position.

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": "ztf_objects_near"
  }
}

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

C2.9/5.0

Behavior2/5

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

Annotations already declare readOnly, idempotent, and openWorld, so the description adds nothing on safety or side effects. It names the upstream source (ALeRCE) but says nothing about coverage, radius limits, result caps, or ordering.

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?

A single tight sentence with the key qualifiers (ZTF, ALeRCE, radius, position) up front. It is efficient, though borderline under-specified rather than deliberately terse.

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 return values need not be explained. However, for a positional cross-match tool sitting among many overlapping catalog siblings, the definition leaves the agent without guidance on selection or on coordinate conventions.

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 description coverage is 0%, so the description carries the burden for three parameters. 'Within radius of a position' at least signals that radius_arcsec controls the search extent, but there are no units or conventions for ra/dec (degrees vs hours) and no mention of the 5-arcsec default.

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?

States the resource (ZTF objects via ALeRCE) and the operation (spatial cone search around a position), which is enough to separate it from ztf_lightcurve. It is a noun phrase rather than a verb, but the meaning is unambiguous.

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?

No indication of when to use this versus ztf_lightcurve, simbad, tns_object, or whats_here, all of which could plausibly be queried at a position. Nothing tells the agent when this tool is the right choice.

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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