Rebrickable

Parts

parts

Read-onlyIdempotent

Search Rebrickable LEGO parts by keyword, color_id, or part_cat_id. Returns part number, name, part category, and image URL. Use colors or category list to get valid IDs.

Input Schema

Name	Required	Description	Default
`page`	No
`query`	No
`color_id`	No
`ordering`	No
`page_size`	No
`part_cat_id`	No

Output Schema

Name	Required	Description
`next`	No	URL to next page of results
`count`	No	Total number of parts matching criteria
`results`	No	Array of part objects
`previous`	No	URL to previous page of results

Schema Changelog

Changes observed during successful MCP inspections.

Changed2 schema fields changedMay 22, 2026

addedInput schema / examples

Added value: +[
+  {
+    "query": "brick 2x4"
+  },
+  {
+    "color_id": 1,
+    "ordering": "part_num",
+    "part_cat_id": 1
+  }
+]

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "count": {
+      "description": "Total number of parts matching criteria",
+      "type": "number"
+    },
+    "next": {
+      "description": "URL to next page of results",
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "previous": {
+      "description": "URL to previous page of results",
+      "type": [
+        "string",
+        "null"
+      ]
+    },
+    "results": {
+      "description": "Array of part objects",
+      "items": {
+        "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"
+      },
+      "type": "array"
+    }
+  },
+  "type": "object"
+}

First observedMay 20, 2026

TDQS

A3.7/5.0

Behavior3/5

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

Annotations already declare readOnlyHint, openWorldHint, idempotentHint, and destructiveHint. Description adds return fields but no additional behavioral traits like pagination or ordering behavior.

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?

Two sentences, front-loaded with purpose and return, followed by a usage tip. No unnecessary words.

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

Completeness2/5

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

Despite output schema existing, the description fails to explain pagination and ordering parameters, which are essential for effective use. Many parameters lack any description.

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?

With 0% schema description coverage, description must explain parameters. It covers 'query', 'color_id', and 'part_cat_id' but ignores 'page', 'page_size', and 'ordering', leaving them unspecified.

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?

Clearly states the tool searches Rebrickable LEGO parts by keyword, color_id, or part_cat_id, and lists return fields. Distinguishes from siblings like 'part' (singular) and 'colors'.

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

Usage Guidelines4/5

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

Provides guidance to use 'colors' or category list to get valid IDs, but does not explicitly state when to avoid this tool (e.g., for a single part, use 'part' tool). Still helpful.

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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