The language of the Rambam (Mishneh Torah, Chapter 7 of Laws of Chametz and Matzah, Halacha 5): "And all these things are called the Haggadah."

In the Shulchan Aruch HaRav (Orach Chayim, Chapter 473, Section 43), it is divided that there is a text that must be said by the letter of the law, and there is one from the perspective of custom, and this is its language. The primary text of the Haggadah that the Sages instituted as obligatory for everyone is from 'Avadim Hayinu' until 'Harei Zeh Meshubach', and then 'Mitechila Ovdei Avodah Zarah Hayu Avoteinu,' until the end of the exposition of the passage 'Arami Oved Avi,' and then 'Pesach Shehayu Ochlim,' 'Matzah Zu,' 'Maror Zeh,' 'Bekol Dor Vador,' 'V'otanu Hotzi Misham,' therefore,' until 'Baruch Atah Hashem Ga'al Yisrael.' The rest of the text of the Haggadah is a custom that all of Israel has practiced from the early generations, etc. Perhaps it depends on whether the recitation of the Haggadah is considered praise, as then a fixed text like the Hallel is required, as Rashi explains regarding Gideon: "Last night, my father was called" when Israel left Egypt.

The Chatam Sofer wrote in his Pesach discourses that one should not recount through pilpul (hair-splitting analysis): "It is a commandment for us to recount the Exodus from Egypt. I have already written that the matter of recounting is not to analyze halachically, for such analysis is clearly from impurity, and therefore on all nights we eat chametz and matzah, for chametz is gematria of division, hinting at the dispute of the enemies in the gate in order to become the matzah of peace in the end, matzah is the gematria of the opposite of division, for in the end, they became loving towards each other. However, this night, the night of vigil, has no hold on impurity, all matzah and peace, only to recount the wonders of the Lord and His miracles." In practice, the Chatam Sofer behaved as written in his customs: "All his length was with the young boys and girls, and he translated every word of the Haggadah for them and explained the content of the matter, and did not say any exposition at all."

The Ga'ri"sh ruled that even pilpul is good for recounting the story of the Exodus from Egypt.

Several interpretations have been given for the meaning of the language of the Haggadah. In the book Chasidei, it was explained as from the word "megadim." This is similar to Rashi's explanation (Deuteronomy 33:13): "From 'megad' - meaning delicacies and sweet." The Abarbanel (Seder Hagadah U'feyrusha) wrote: "And it is called the Haggadah, from the verse 'And you shall tell your son on that day,' (Exodus 13:8). Furthermore, because it tells of the matter of the Exodus from Egypt, the miracles and wonders that the Holy One, blessed be He, did for us at that time. Some explain the Haggadah as a language of acknowledgment and praise to the Almighty for taking us out of the land of Egypt, as translated in the Jerusalem Talmud Hagadati today to the Lord your God (Deuteronomy 26:3) - 'you praised the day of judgment.' So too, Rabbi Saadia translated it in Arabic."

According to this, the foundation of the Haggadah is to acknowledge and praise the Almighty out of gratitude for the miracles, wonders, and redemption. The Haggadah is derived from the section of the first fruits, as their entire purpose is gratitude. We also find the language "to tell of Your kindness in the morning" (Psalms 92:3), which means to thank for the good and kindness. This is also mentioned in Berachot (12a), that one should say "emet v'yatziv" in the morning because of "to tell of Your kindness in the morning," and Rashi explained it as praise to the Holy One, blessed be He, for the Exodus from Egypt. This is also found in the language of the Rambam (Sefer Hamitzvot, Positive Commandment 137), which includes the language of acknowledgment in the commandment of recounting the Exodus from Egypt