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alistaircroll
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understand-ckan

Documents the CKAN Action API endpoints, pagination, and conventions for Montréal's open data portal.

1|Updated Mar 13, 2026
Search Tags:#sql#api reference#pagination#datastore#open data#ckan#montreal
One-click install
npx skills add https://github.com/alistaircroll/montreal-open-data --skill understand-ckan-alistaircroll
Or copy as Structured Prompt for Agent▼
Please help me install this Agent Skill.
Skill: understand-ckan
Source: https://github.com/alistaircroll/montreal-open-data/tree/main/skills/core/understand-ckan
Command: npx skills add https://github.com/alistaircroll/montreal-open-data --skill understand-ckan-alistaircroll

SYSTEM DOCUMENTATION & REQUIREMENTS

What problem does it solve? Working with Montréal's open data portal requires understanding the CKAN Action API's structure, endpoints, and quirks. This Skill provides a complete bilingual reference so an AI agent can correctly query donnees.montreal.ca without trial-and-error or misinterpreting API responses. ## Core Features & Use Cases - Three API Layers Documented: Covers the Action API for catalog metadata, the DataStore API for SQL and filtered queries on tabular data, and the FileStore API for raw file downloads. - Gotchas & Edge Cases: Explains critical details like the 32,000-row DataStore limit, UUID-based resource IDs, double-quoted SQL column names, and French-dominant metadata. - Use Case: When asked "How many trees are in the Plateau?", the agent uses this reference to construct a correct datastore_search_sql call with proper quoting, pagination, and filter syntax against the tree dataset's resource UUID. ## Quick Start Ask the agent to explain how to query a dataset on donnees.montreal.ca using the CKAN DataStore API with filters and pagination.

Frequently Asked Questions about understand-ckan

High-intent search queries and answers about installing and using this skill.

FAQPage Schema
How do I query Montréal open data with the CKAN API?▼

Use the DataStore API endpoint datastore_search with a resource UUID, optional filters as a JSON object, and limit/offset for pagination. For full SQL, use datastore_search_sql with the resource UUID as the double-quoted table name.

How do I search for datasets on donnees.montreal.ca?▼

Use the package_search endpoint with a q parameter for keywords, plus field-specific filters like organization:ville-de-montreal or tags:Transport. Control result size with rows and start parameters for pagination.

Does the CKAN API require an API key for reading data?▼

No authentication is required for read operations on Montréal's CKAN portal. All Action API endpoints accept GET or POST requests without credentials, returning JSON with a success flag and result payload.

Why does my CKAN SQL query fail on column names?▼

CKAN DataStore SQL requires double quotes around column names containing accents, spaces, or mixed case, such as "Essence_fr". The table name must also be the resource UUID in double quotes, and JOINs across resources are not supported.

What is the row limit for CKAN DataStore queries?▼

DataStore queries return at most 32,000 rows per request. For larger datasets like the 333,556-record tree inventory, paginate using the offset and limit parameters across multiple requests.

Can I query GeoJSON or Shapefile resources through the DataStore API?▼

No. Only resources with datastore_active set to true are queryable. GeoJSON, Shapefile, PDF, and GBFS resources must be downloaded directly via the FileStore download URL pattern instead.

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