query_data
Execute SELECT queries on SQLite databases to retrieve and analyze data, enabling AI assistants to interact with database content through structured queries.
Instructions
Execute a SELECT query on the database
Input Schema
TableJSON Schema
| Name | Required | Description | Default |
|---|---|---|---|
| query | Yes | SQL SELECT query to execute | |
| limit | No | Maximum number of rows to return |
Implementation Reference
- src/index.ts:289-340 (handler)The handler function that executes SELECT queries on the SQLite database, enforces SELECT-only, applies LIMIT if missing, formats results as a markdown-like table, and returns as CallToolResult.
private async queryData(args: { query: string; limit?: number }): Promise<CallToolResult> { if (!this.db) { throw new Error("No database connected. Use connect_database first."); } try { // Ensure it's a SELECT query const trimmedQuery = args.query.trim().toLowerCase(); if (!trimmedQuery.startsWith("select")) { throw new Error("Only SELECT queries are allowed with query_data. Use execute_query for other operations."); } const limit = args.limit || 100; const queryWithLimit = args.query.toLowerCase().includes("limit") ? args.query : `${args.query} LIMIT ${limit}`; const results = this.db.prepare(queryWithLimit).all(); if (results.length === 0) { return { content: [ { type: "text", text: "Query executed successfully. No rows returned.", } satisfies TextContent, ], }; } // Format results as a table const headers = Object.keys(results[0] as Record<string, unknown>); const rows = results.map((row) => headers.map(header => String((row as Record<string, unknown>)[header] ?? "NULL")).join(" | ") ); const headerRow = headers.join(" | "); const separator = headers.map(h => "-".repeat(h.length)).join("-|-"); const table = [headerRow, separator, ...rows].join("\n"); return { content: [ { type: "text", text: `Query results (${results.length} rows):\n\n${table}`, } satisfies TextContent, ], }; } catch (error) { throw new Error(`Query failed: ${error instanceof Error ? error.message : String(error)}`); } } - src/index.ts:103-117 (schema)Input schema definition for the query_data tool, specifying 'query' as required string and optional 'limit' number.
inputSchema: { type: "object", properties: { query: { type: "string", description: "SQL SELECT query to execute", }, limit: { type: "number", description: "Maximum number of rows to return", default: 100, }, }, required: ["query"], }, - src/index.ts:101-118 (registration)Tool registration in the listTools response, including name, description, and input schema.
name: "query_data", description: "Execute a SELECT query on the database", inputSchema: { type: "object", properties: { query: { type: "string", description: "SQL SELECT query to execute", }, limit: { type: "number", description: "Maximum number of rows to return", default: 100, }, }, required: ["query"], }, }, - src/index.ts:171-172 (registration)Dispatcher in callToolRequestHandler switch statement that routes query_data calls to the queryData handler method.
case "query_data": return await this.queryData(args as { query: string; limit?: number });