mcp-sqlserver

Instructions

Implementation Reference

• src/index.ts:215-247 (registration)

  Tool registration for 'describe_table' with MCP server, including description and input schema definition using zod.

  mcp.registerTool(
    "describe_table",
    {
      description: "Return column names and types for a table.",
      inputSchema: {
        table: z.string().describe("Table name (e.g. dbo.MyTable or MyTable)"),
        schema: z.string().optional().describe("Schema name (e.g. dbo). Defaults to dbo if table has no schema prefix."),
      },
    },
    async ({ table, schema }) => {
      try {
        const p = await getPool();
        const schemaName = schema ?? "dbo";
        const query = `
          SELECT COLUMN_NAME, DATA_TYPE, CHARACTER_MAXIMUM_LENGTH, IS_NULLABLE
          FROM INFORMATION_SCHEMA.COLUMNS
          WHERE TABLE_SCHEMA = @schema AND TABLE_NAME = @table
          ORDER BY ORDINAL_POSITION
        `;
        const result = await p
          .request()
          .input("schema", sql.NVarChar(128), schemaName)
          .input("table", sql.NVarChar(128), table)
          .query(query);
        const rows = (result.recordset ?? []) as Record<string, unknown>[];
        const text = formatTable(rows);
        return { content: [{ type: "text" as const, text }] };
      } catch (err) {
        const msg = err instanceof Error ? err.message : String(err);
        return { content: [{ type: "text" as const, text: `Error: ${msg}` }], isError: true };
      }
    }
  );

• src/index.ts:224-246 (handler)

  Handler function that queries INFORMATION_SCHEMA.COLUMNS to retrieve column names, data types, max length, and nullability for a specified table.

  async ({ table, schema }) => {
    try {
      const p = await getPool();
      const schemaName = schema ?? "dbo";
      const query = `
        SELECT COLUMN_NAME, DATA_TYPE, CHARACTER_MAXIMUM_LENGTH, IS_NULLABLE
        FROM INFORMATION_SCHEMA.COLUMNS
        WHERE TABLE_SCHEMA = @schema AND TABLE_NAME = @table
        ORDER BY ORDINAL_POSITION
      `;
      const result = await p
        .request()
        .input("schema", sql.NVarChar(128), schemaName)
        .input("table", sql.NVarChar(128), table)
        .query(query);
      const rows = (result.recordset ?? []) as Record<string, unknown>[];
      const text = formatTable(rows);
      return { content: [{ type: "text" as const, text }] };
    } catch (err) {
      const msg = err instanceof Error ? err.message : String(err);
      return { content: [{ type: "text" as const, text: `Error: ${msg}` }], isError: true };
    }
  }

• src/index.ts:219-222 (schema)

  Input schema validation defining 'table' (required) and 'schema' (optional) parameters for the describe_table tool.

  inputSchema: {
    table: z.string().describe("Table name (e.g. dbo.MyTable or MyTable)"),
    schema: z.string().optional().describe("Schema name (e.g. dbo). Defaults to dbo if table has no schema prefix."),
  },