Rebrickable

Part

part

Read-onlyIdempotent

Fetch details for a single LEGO part by part_num from Rebrickable. Returns part name, category, material, and image URLs across available colors.

Input Schema

Name	Required	Description	Default
`part_num`	Yes

Output Schema

Name	Required	Description
`name`	No	Part name
`year_to`	No	Year part was last produced
`part_num`	No	Part number identifier
`part_url`	No	Rebrickable URL for part
`year_from`	No	Year part was first produced
`part_cat_id`	No	Part category ID
`part_img_url`	No	Image URL for part
`part_cat_name`	No	Part category name

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedMay 22, 2026

addedInput schema / examples

Added value: +[
+  {
+    "part_num": "3001"
+  }
+]

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "name": {
+      "description": "Part name",
+      "type": "string"
+    },
+    "part_cat_id": {
+      "description": "Part category ID",
+      "type": "number"
+    },
+    "part_cat_name": {
+      "description": "Part category name",
+      "type": "string"
+    },
+    "part_img_url": {
+      "description": "Image URL for part",
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "part_num": {
+      "description": "Part number identifier",
+      "type": "string"
+    },
+    "part_url": {
+      "description": "Rebrickable URL for part",
+      "type": "string"
+    },
+    "year_from": {
+      "description": "Year part was first produced",
+      "type": [
+        "number",
+        "null"
+      ]
+    },
+    "year_to": {
+      "description": "Year part was last produced",
+      "type": [
+        "number",
+        "null"
+      ]
+    }
+  },
+  "type": "object"
+}

First observedMay 20, 2026

TDQS

A4.2/5.0

Behavior4/5

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint=false. The description adds that the tool returns specific fields (name, category, material, image URLs), which is useful context beyond annotations. No contradictions.

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 a single, well-structured sentence. It front-loads the core action and key parameter, then enumerates return fields. No wasted words.

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

Completeness4/5

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

Given the tool's simplicity (1 param, has output schema), the description covers essential details. It mentions returned fields, and the output schema can provide further structure. Adequate for an agent to use correctly.

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?

Schema description coverage is 0%, but the description explains that `part_num` is the identifier for the part, adding meaning beyond the schema's simple type declaration.

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 the tool fetches details for a single LEGO part by part_num, specifying returned fields (name, category, material, image URLs). This distinguishes it from sibling tools like 'parts' which likely list multiple parts.

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

Usage Guidelines3/5

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

The description implies use when you need a specific part's details, but lacks explicit comparison to siblings like 'parts' for listing or 'colors' for color-specific queries. No direct guidance on when not to use it.

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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