Catfacts

Get Fact

get_fact

Read-onlyIdempotent

Get a random cat fact. Returns the fact text and character length. Use get_facts to retrieve multiple facts at once.

Example tool call

This call uses example arguments supplied in the tool’s input schema.

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

Input Schema

Name	Required	Description	Default
No arguments

Output Schema

Name	Required	Description	Default
`fact`	Yes	The cat fact text
`length`	Yes	Character length of the fact

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedMay 8, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "fact": {
+      "description": "The cat fact text",
+      "type": "string"
+    },
+    "length": {
+      "description": "Character length of the fact",
+      "type": "number"
+    }
+  },
+  "required": [
+    "fact",
+    "length"
+  ],
+  "type": "object"
+}

Changed1 schema field changedMay 6, 2026
- addedInput schema / examples
```
Added value: +[
+  {}
+]
```
First observedApr 14, 2026

TDQS

A4.7/5.0

Behavior4/5

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

Annotations already declare readOnlyHint, idempotentHint, and non-destructive behavior, so the safety profile is covered. The description adds the 'random' nature of the fact and the specific return fields (fact text and character length), which are behavioral details beyond the annotations. It does not mention any edge cases, but for a simple read-only tool this is sufficient.

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 two sentences, front-loaded with the primary action, then the return value, and finally the alternative. Every sentence contributes meaningful information with no redundancy or filler.

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?

For a zero-parameter tool with strong annotations (read-only, idempotent, non-destructive) and a defined output schema, the description provides sufficient detail: what it does, what it returns, and when to use the sibling tool. There are no gaps for this level of complexity.

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 has zero parameters and the schema coverage is 100%, so there are no parameter semantics to explain. The baseline for zero parameters is 4; no additional explanation is needed or provided. The description does not need to add parameter information.

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 clearly states 'Get a random cat fact' with a specific verb and resource, and further specifies what is returned ('fact text and character length'). It also distinguishes from the sibling tool get_facts by indicating this one retrieves a single fact. This is a clear, specific purpose.

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?

The description explicitly says 'Use get_facts to retrieve multiple facts at once,' providing direct guidance on when to use this tool versus the alternative. This is explicit and actionable usage guidance.

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

All Catfacts tools Inspect

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