Clickhouse
Tools to query and explore a ClickHouse database
1.0.1ClickHouse Toolkit
Arcade's ClickHouse toolkit connects agents to a ClickHouse database, enabling structured discovery and read-only querying of its contents.
Capabilities
- Database & table discovery — enumerate available databases and tables before constructing any query; a default schema stub is returned for schema-level introspection (ClickHouse has no PostgreSQL-style schemas).
- Schema inspection — retrieve the exact column names, types, and structure of any table prior to querying.
- Read-only SQL execution — run parameterized
SELECTqueries with explicit clause parts (select, from, join, where, having, order by, limit, offset);INSERT,UPDATE,DELETE, and DDL are blocked. - Query safety guardrails — enforced rules include no
SELECT *, mandatory ordering, case-insensitive string matching, trimming,LIKE-preferred matching, and index/primary-key-only joins.
Secrets
CLICKHOUSE_DATABASE_CONNECTION_STRING — A connection string used to authenticate and connect to your ClickHouse instance. The format is typically a DSN or URL that includes the protocol, host, port, username, password, and target database, for example: clickhouse://user:password@host:8123/database. You can construct this string from your ClickHouse cluster credentials found in your hosting provider's dashboard (e.g., ClickHouse Cloud console under Connection Details, or your self-hosted server configuration). Ensure the credentials belong to a user with at least SELECT privileges on the target database.
For how to store and reference secrets in Arcade, see the Arcade secrets guide. You can manage secrets directly at https://api.arcade.dev/dashboard/auth/secrets.
Available tools(5)
| Tool name | Description | Secrets | |
|---|---|---|---|
Discover all the databases in the ClickHouse database. | 1 | ||
Discover all the schemas in the ClickHouse database.
Note: ClickHouse doesn't have schemas like PostgreSQL, so this returns a default schema name. | 1 | ||
Discover all the tables in the ClickHouse database when the list of tables is not known.
ALWAYS use this tool before any other tool that requires a table name. | 1 | ||
You have a connection to a ClickHouse database.
Execute a SELECT query and return the results against the ClickHouse database.
No other queries (INSERT, UPDATE, DELETE, etc.) are allowed.
ONLY use this tool if you have already loaded the schema of the tables you need to query.
The final query will be constructed as follows:
SELECT {select_query_part} FROM {from_clause} JOIN {join_clause}
WHERE {where_clause} HAVING {having_clause}
ORDER BY {order_by_clause} LIMIT {limit} OFFSET {offset}
When running queries, follow these rules which will help avoid errors:
* Never "select *" from a table. Always select the columns you need.
* Always order your results. Use the most important columns or the primary key if you're unsure.
* Always use case-insensitive queries to match strings in the query.
* Always trim strings in the query.
* Prefer LIKE queries over direct string matches or regex queries.
* Only join on columns that are indexed or the primary key. Do not join on arbitrary columns.
* ClickHouse is case-sensitive, so be careful with table and column names. | 1 | ||
Get the schema/structure of a ClickHouse table in the ClickHouse database
when the schema is not known, and the name of the table is provided.
This tool should ALWAYS be used before executing any query.
All tables in the query must be discovered first,
so that their exact names are known. | 1 |