Opendata Canada

Groups

groups

Read-onlyIdempotent

List the subject-area themes used across open.canada.ca (e.g. Nature And Environment, Science And Technology, Health And Safety), ranked by dataset count. Each theme includes an fq filter string to pass to the search tool to list that theme's datasets. Use this to browse what Canada publishes by topic before searching.

Input Schema

TableJSON Schema

Name	Required	Description	Default
`limit`	No

Output Schema

TableJSON Schema

Name	Required	Description
`note`	No	Explanatory note about the theme source
`count`	Yes	Number of themes returned
`groups`	Yes	Themes from the Solr `subject` facet.
`total_datasets`	No	Total datasets across the portal

Schema Changelog

Changes observed during successful MCP inspections.

Changed6 schema fields changedAug 3, 2026

changedOutput schema / properties / count / description

Previous value: -"Number of items returned."New value: +"Number of themes returned"

addedOutput schema / properties / groups

Added value: +{
+  "description": "Themes from the Solr `subject` facet.",
+  "items": {
+    "properties": {
+      "datasets": {
+        "description": "Number of datasets carrying this theme",
+        "type": "integer"
+      },
+      "fq": {
+        "description": "Solr filter query that reproduces this theme, e.g. subject:\"transport\"",
+        "type": "string"
+      },
+      "name": {
+        "description": "Theme name",
+        "type": "string"
+      },
+      "title": {
+        "description": "Human-readable theme title",
+        "type": "string"
+      }
+    },
+    "type": "object"
+  },
+  "type": "array"
+}

removedOutput schema / properties / items

Removed value: -{
-  "description": "List of themes/groups",
-  "items": {
-    "properties": {
-      "created": {
-        "description": "Creation timestamp",
-        "type": "string"
-      },
-      "description": {
-        "description": "Group/theme description",
-        "type": "string"
-      },
-      "id": {
-        "description": "Group/theme ID",
-        "type": "string"
-      },
-      "image_display_url": {
-        "description": "Group image URL",
-        "type": "string"
-      },
-      "name": {
-        "description": "Group/theme name",
-        "type": "string"
-      },
-      "title": {
-        "description": "Group/theme title",
-        "type": "string"
-      }
-    },
-    "type": "object"
-  },
-  "type": "array"
-}

addedOutput schema / properties / note

Added value: +{
+  "description": "Explanatory note about the theme source",
+  "type": "string"
+}

addedOutput schema / properties / total_datasets

Added value: +{
+  "description": "Total datasets across the portal",
+  "type": "integer"
+}

changedOutput schema / required

Previous value: -[
-  "items",
-  "count"
-]New value: +[
+  "groups",
+  "count"
+]

Changed2 schema fields changedMay 27, 2026

addedInput schema / examples

Added value: +[
+  {
+    "limit": 15
+  }
+]

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "properties": {
+    "count": {
+      "description": "Number of items returned.",
+      "type": "integer"
+    },
+    "items": {
+      "description": "List of themes/groups",
+      "items": {
+        "properties": {
+          "created": {
+            "description": "Creation timestamp",
+            "type": "string"
+          },
+          "description": {
+            "description": "Group/theme description",
+            "type": "string"
+          },
+          "id": {
+            "description": "Group/theme ID",
+            "type": "string"
+          },
+          "image_display_url": {
+            "description": "Group image URL",
+            "type": "string"
+          },
+          "name": {
+            "description": "Group/theme name",
+            "type": "string"
+          },
+          "title": {
+            "description": "Group/theme title",
+            "type": "string"
+          }
+        },
+        "type": "object"
+      },
+      "type": "array"
+    }
+  },
+  "required": [
+    "items",
+    "count"
+  ],
+  "type": "object"
+}

First observedMay 18, 2026

TDQS

A4.3/5.0

Behavior4/5

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

Annotations already mark this as a safe read operation. The description adds useful behavioral context (ranking, inclusion of fq filter, coverage of open.canada.ca) without contradicting the annotations.

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 concise sentences deliver the core purpose, example themes, and usage guidance with no unnecessary fluff. Information is front-loaded and every sentence earns its place.

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?

The tool is simple, has an output schema, and the description covers purpose, context, and how to use the result with another tool. The only gap is the undocumented 'limit' parameter, but given the simplicity and output schema, overall completeness is strong.

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?

The schema has only one parameter (limit) with zero description coverage. The description does not mention 'limit' at all, leaving the agent to infer its meaning. Since coverage is low, the description should compensate, but it does not.

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 lists subject-area themes from open.canada.ca, ranked by dataset count, and provides an fq filter for use with the search tool. This distinguishes it from siblings like 'organizations' and clarifies its role in the browsing/search workflow.

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?

It explicitly instructs to use this tool to browse themes before searching, and explains that the fq filter should be passed to the search tool. This gives a clear when-to-use and prescriptive usage, going beyond basic context.

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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