Vigi-Sky

Hatch archive statistics

hatch_stats

Read-onlyIdempotent

Return aggregate statistics of the Hatch UFO archive (18,116 cases, 1900-2002): cases by decade and top countries. Use it for the big picture of historical reports; for cases near a place use nearby_cases. Archive data, not 2026 sightings; live read of the Vigi-Sky API.

Tool call template

This tool declares no required parameters. Add optional parameters from the input schema as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {},
    "name": "hatch_stats"
  }
}

Input Schema

Name	Required	Description	Default
No arguments

Output Schema

Name	Required	Description	Default
`n`	No
`archive`	No
`citations`	Yes
`provenance`	Yes
`top_countries`	No
`by_decade_1900_2002`	No

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedNov 2, 2026

addedOutput schema / description

Added value: +"Returns archive, n, by_decade_1900_2002, top_countries, citations, provenance."

Changed7 schema fields changedAug 18, 2026
- addedOutput schema / properties / archive
```
Added value: +{
+  "type": "string"
+}
```
- addedOutput schema / properties / by_decade_1900_2002
```
Added value: +{
+  "type": "object"
+}
```
- removedOutput schema / properties / doctrine
```
Removed value: -{
-  "type": "string"
-}
```
- addedOutput schema / properties / n
```
Added value: +{
+  "type": [
+    "integer",
+    "null"
+  ]
+}
```
- addedOutput schema / properties / provenance / properties / never
```
Added value: +{
+  "type": "string"
+}
```
- addedOutput schema / properties / top_countries
```
Added value: +{
+  "type": "object"
+}
```
- addedOutput schema / required
```
Added value: +[
+  "citations",
+  "provenance"
+]
```
First observedAug 17, 2026

TDQS

A4.7/5.0

Behavior4/5

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

Annotations already declare readOnly, idempotent, non-destructive and openWorld, so the safety profile is covered. The description still adds meaningful context beyond them: the data provenance (archival 1900-2002 corpus, not live 2026 sightings) and that it is a live read of the Vigi-Sky API, which implies availability/latency dependence. It stops short of stating rate limits or failure behavior, so not a 5.

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?

Three short clauses, front-loaded with what is returned and its scope, followed by the routing hint and the data-provenance caveat. Every sentence carries information an agent needs; nothing is repeated from the schema or annotations.

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

Completeness5/5

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

An output schema exists, so return shape needn't be described, and the description already names the two aggregate dimensions (by decade, top countries). Combined with the corpus size, date range, provenance caveat and sibling routing, nothing material is missing for a zero-parameter read tool.

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

Parameters4/5

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

The tool takes no parameters, so the baseline is 4 and there is nothing for the description to disambiguate. It does not, and need not, explain inputs.

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 a specific verb and resource plus exact scope: aggregate statistics of the Hatch UFO archive, 18,116 cases from 1900-2002, broken down by decade and top countries. It explicitly separates itself from the sibling nearby_cases, so an agent can choose between the two without opening either schema.

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

Usage Guidelines5/5

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

"Use it for the big picture of historical reports; for cases near a place use nearby_cases" gives an explicit when-to-use plus the named alternative and its selection condition. "Archive data, not 2026 sightings" adds a clear exclusion so the agent does not mistake it for current sighting data.

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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