ClickHouse Readonly MCP

Overview

The ClickHouse Readonly MCP is a lightweight FastMCP server designed to expose read‑only access to ClickHouse databases for AI assistants. By wrapping the database behind a secure, validated interface, it lets Claude or other MCP‑compatible agents run ad‑hoc queries without risking data modification or accidental schema changes. The server validates each request, allowing only SELECT, SHOW, DESCRIBE, and EXPLAIN statements, thereby providing a safety net for environments that require strict read‑only access.

Developers benefit from two modes of operation: a local Python API that can be invoked directly in their codebase, and a standalone service that listens for MCP requests over HTTP. This duality means the same logic can be reused in both scripted workflows and production deployments, reducing duplication of effort. The server automatically selects between a native TCP connection or the HTTP interface depending on configuration, ensuring optimal performance while maintaining high availability.

Key capabilities include parameterized queries, which let agents safely inject user input into SQL statements; a concise tabular output format that is easy for downstream models to parse; and an optional resource description file that enriches the assistant’s understanding of table semantics. By supplying metadata such as “this table stores user activity logs,” the assistant can generate more accurate queries and explanations. The server also incorporates a fail‑over strategy that switches to the HTTP endpoint if the native port is unreachable, minimizing downtime.

Typical use cases involve data‑driven conversational agents that need to answer questions about business metrics, audit logs, or analytical dashboards. For example, a sales chatbot can query quarterly revenue directly from ClickHouse and present the result in natural language. In another scenario, a compliance tool can let an AI audit recent changes by running SHOW TABLES or DESCRIBE queries, ensuring that only permissible actions are performed. Because the MCP server enforces read‑only operations, it is ideal for regulated environments where accidental writes could violate compliance policies.

Integrating the ClickHouse Readonly MCP into an AI workflow is straightforward: developers configure the MCP client to point at the server’s endpoint, supply any necessary authentication tokens, and then issue SQL queries as tools. The assistant receives the result set in a structured format that can be fed back into prompt templates or visualized by downstream components. This seamless bridge between conversational AI and high‑performance analytical databases enables rapid prototyping, real‑time analytics, and secure data exploration—all while keeping the underlying database protected from unintended modifications.