MCP-Turso

Instructions

Implementation Reference

• src/utils.ts:50-76 (handler)

  Core handler function that executes PRAGMA table_info to retrieve and map detailed column information for the specified table.

  export async function describeTable(
  	tableName: string,
  	client: Client,
  ): Promise<TableColumn[]> {
  	if (!/^[a-zA-Z0-9_]+$/.test(tableName)) {
  		throw new Error(
  			"Invalid table name. Only alphanumeric characters and underscores are allowed.",
  		);
  	}
  
  	const result = await client.execute({
  		sql: `PRAGMA table_info(${tableName})`,
  		args: [],
  	});
  
  	if (result.rows.length === 0) {
  		throw new Error(`Table '${tableName}' not found`);
  	}
  
  	return result.rows.map((row) => ({
  		name: row.name as string,
  		type: row.type as string,
  		notnull: row.notnull as number,
  		dflt_value: row.dflt_value as string | null,
  		pk: row.pk as number,
  	}));
  }

• src/index.ts:83-105 (registration)

  Registers the describe_table tool with FastMCP server, defining name, description, input parameters schema, and execute wrapper that calls the handler.

  server.addTool({
  	name: "describe_table",
  	description: "View schema information for a specific table",
  	parameters: z.object({
  		table_name: z
  			.string()
  			.describe("Name of the table to describe")
  			.min(1, "Table name is required"),
  	}),
  	execute: async ({ table_name }) => {
  		try {
  			logger.info(`Executing describe_table for table: ${table_name}`);
  			const schema = await describeTable(table_name, db);
  			return content(JSON.stringify({ schema }, null, 2));
  		} catch (error) {
  			logger.error(`Failed to describe table ${table_name}`, error);
  			return content(
  				`Error describing table: ${error instanceof Error ? error.message : String(error)}`,
  				true,
  			);
  		}
  	},
  });

• src/types.ts:3-11 (schema)

  Zod schema and TypeScript type definition for TableColumn, used as the return type of the describeTable handler.

  export const TableColumnSchema = z.object({
  	name: z.string(),
  	type: z.string(),
  	notnull: z.number(),
  	dflt_value: z.union([z.string(), z.null()]),
  	pk: z.number(),
  });
  
  export type TableColumn = z.infer<typeof TableColumnSchema>;