Siman 112
Presented here for study, not as a practical ruling. The Shulchan Aruch rules by Sephardi custom, the Rema's glosses by Ashkenazi custom, and the Kitzur follows Ashkenazi custom. For a practical question, ask your rabbi.
א אַל יִשְׁאַל אָדָם צְרָכָיו בְּג' רִאשׁוֹנוֹת, וְלֹא בְּג' אַחֲרוֹנוֹת; וְדַוְקָא צָרְכֵי יָחִיד, אֲבָל צָרְכֵי צִבּוּר שָׁרֵי.
1 That One Should Not Interrupt [the Amidah], Neither In The First Three [Blessings] Nor in the Final Three. Containing 2 Se'ifim: One should not ask for one's needs in the first three [blessings of the Amidah] nor in the final three. And this is specifically [regarding] the needs of the individual, but [for the] needs of the community, it is permitted.
ב אֵין לוֹמַר פִּיּוּטִים וְלֹא קְרוֹבֵץ (פי' קְרוֹבֵץ לְיוֹצֵר, וְיֵשׁ אוֹמְרִים שֶׁהוּא רָאשֵׁי תֵּבוֹת קוֹל רִנָּה וִישׁוּעָה בְּאָהֳלֵי צַדִּיקִים) בַּתְּפִלָּה. הַגָּה: וְיֵשׁ מַתִּירִין, הוֹאִיל וְצָרְכֵי רַבִּים הֵם (הָרֹא"שׁ וְהַתוס' וְהָר"י וְהָרַ"ן רֵישׁ פ' בַּתְרָא דְּרֹאשׁ הַשָּׁנָה וְהַגָּהוֹת מַיְמוֹנִי פֶּרֶק י' וְטוּר), וְכֵן נוֹהֲגִים בְּכָל מָקוֹם לְאָמְרָם.
2 One should not say liturgical poems nor a "krovetz" (meaning "krovot l'Yotzeir" [close to the blessing of Yotzeir Or], and some say it is an acronym for "Kol Rina Vi-shua B'ohalei Tzadikim" [Psalms 118:15]) during the prayer [i.e. Amidah]. Rema: And there are those who permit [them], since they are [considered] needs of the public (the Rosh; Tosefot; the Ri; and the Ran at the beginning of the last chapter of Tractate Rosh Hashana; and Hagahot Maimoni, chapter 10; and the Tur), and such it is practiced in all places to say them.