Execute a SPARQL SELECT query against any public HTTPS SPARQL endpoint. Useful for querying open data portals and knowledge graphs that expose SPARQL endpoints, including: - data.europa.eu (European open data portal) - publications.europa.eu (EU Publications Office) - DBpedia, Wikidata - Any DCAT...
Risk signalsAccepts freeform code/query input (query)
Part of the Ckan server.
Free to start. No card required.
AI agents call sparql_query to retrieve information from Ckan without modifying any data. This is common in research, monitoring, and reporting workflows where the agent needs context before taking action. Because read operations don't change state, they are generally safe to allow without restrictions -- but you may still want rate limits to control API costs.
Even though sparql_query only reads data, uncontrolled read access can leak sensitive information or rack up API costs. An agent caught in a retry loop could make thousands of calls per minute. A rate limit gives you a safety net without blocking legitimate use.
Read-only tools are safe to allow by default. No rate limit needed unless you want to control costs.
{
"version": "1",
"default": "deny",
"tools": {
"sparql_query": {}
}
}See the full Ckan policy for all 20 tools.
These attack patterns abuse exactly the kind of access sparql_query gives an agent. Each links to the full case and the policy that stops it:
Other read tools across the catalogue. The same approach applies to each: allow, with a rate cap to control cost.
Execute a SPARQL SELECT query against any public HTTPS SPARQL endpoint. Useful for querying open data portals and knowledge graphs that expose SPARQL endpoints, including: - data.europa.eu (European open data portal) - publications.europa.eu (EU Publications Office) - DBpedia, Wikidata - Any DCAT-AP compliant data catalog Only HTTPS endpoints are allowed. Queries timeout after 15 seconds. Only SELECT queries are supported (read-only). If the query does not contain a LIMIT clause, one is injected automatically (default: 25, max: 1000). Args: - endpoint_url (string): HTTPS URL of the SPARQL endpoint - query (string): SPARQL SELECT query to execute - limit (number): Max rows to return (default: 25). Ignored if query already contains LIMIT. - response_format ('markdown' | 'json'): Output format Examples: - Count Italian HVD datasets by publisher on data.europa.eu - Query Wikidata for entities related to a dataset topic - Explore EU controlled vocabularies on publications.europa.eu Typical workflow: sparql_query (explore schema) → sparql_query (targeted query) → ckan_package_search (get dataset details). It is categorised as a Read tool in the Ckan MCP Server, which means it retrieves data without modifying state.
Register the Ckan MCP server in PolicyLayer and add a rule for sparql_query: allow, deny, rate-limit, or require approval. Point your MCP client at the PolicyLayer proxy URL and the rule is enforced on every call, before it reaches Ckan. Nothing to install.
sparql_query is a Read tool with low risk. Read-only tools are generally safe to allow by default.
Yes. Add a rate_limit block to the sparql_query rule in your PolicyLayer policy. For example, setting max: 10 and window: 60 limits the tool to 10 calls per minute. Rate limits are tracked per agent session and reset automatically.
Set action: deny in the PolicyLayer policy for sparql_query. The AI agent will receive a policy violation error and cannot call the tool. You can also include a reason field to explain why the tool is blocked.
sparql_query is provided by the Ckan MCP server (@aborruso/ckan-mcp-server). PolicyLayer sits as a proxy in front of this server to enforce policies before tool calls reach the server.
Deterministic rules across all 20 Ckan tools. Per-identity grants. Full audit log. Live in minutes. Nothing to install.
Free to start. No card required.
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