AstroMCP

simbad

Read-onlyIdempotent

Find known astronomical objects near a sky position within a specified radius, returning nearest matches with identifiers, object types, spectral types, and redshifts.

Instructions

SIMBAD objects within radius (nearest first): main id, object type, spectral type, redshift.

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": "simbad"
  }
}

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

B3/5.0

Behavior3/5

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

Annotations already declare readOnlyHint, openWorldHint, and idempotentHint, so the safety profile is covered. The description adds useful behavior by stating nearest-first ordering and listing fields, but it omits result limits, coordinate-frame assumptions, maximum radius, and error behavior.

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 description is a single front-loaded sentence with no filler. It is somewhat telegraphic, and the output-field list is partly redundant because an output schema exists, which keeps it below a 5.

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?

For a simple three-parameter read-only cone search with annotations and an output schema, the description is minimally adequate. However, it leaves important input semantics and result-boundary behavior unspecified, which matters given the 0% schema description coverage.

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 description coverage is 0%, so the description needs to compensate for three undocumented parameters. It only says 'within radius' without explaining the RA/Dec frame, radius units despite the parameter name, default radius behavior, or required inputs.

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?

It clearly identifies the resource (SIMBAD objects), the spatial scope (within radius), ordering (nearest first), and returned fields. The catalog name distinguishes it from siblings such as Gaia or ZTF, though it does not explicitly name alternatives.

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 when-to-use or when-not-to-use guidance, and no comparison to alternatives like whats_here, ztf_objects_near, or gaia. The intended use is only implied by naming SIMBAD.

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

Deploy Server