Also read - Extracting details about Islam using the mind

The below narrations indicate that the Safeer (ambassadors) of Imam Mahdi (ع) used to not convey anything of their own opinion, but whatever they said was from the Imams (ع)

Uthman bin Amri & Muhammad bin Uthman:

و قد أخبرنا أحمد بن إسحاق أبو علي عن أبي الحسن ع قال سألته فقلت له لمن أعامل وعمن آخذ و قول من أقبل فقال له العمري ثقتي فما أدى إليك فعني يؤدي و ما قال لك فعني يقول فاسمع له و أطع فإنه الثقة

Narrated that Ahmed bin Ishaq asked Abul Hasan Imam Ali Naqi (ع),

"From whom should I deal with, from whom should I take, and whose saying should I accept (after you)?

Imam (ع) said to him, al-Amri is trustworthy to me. Whatever he will deliver to you is from Me. Whatever he would say to you is from Me. Listen to him and obey him because he is reliable and trustworthy."

[Source: al-Ghaybah, Shaikh Toosi, Pg. 381]

وأخبرني أبو علي أنه سأل أبا محمد الحسن بن علي عن مثل ذلك فقال له: العمري وابنه ثقتان، فما أديا إليك فعني يؤديان، وما قالا لك فعني يقولان، فاسمع لهما وأطعهما فإنهما الثقتان المأمونان

Narrated that Abu Ali asked Abu Muhammad Imam Askari (ع) a similar question and the Imam (ع) said to him,

"al-Amri and his son are trustworthy people. Whatever they deliver to you is from me. Whatever they say to you is from me. Listen to them and obey them because they are trustworthy and reliable people."

[Source: al-Ghaybah, Shaikh Toosi, Pg. 381]

Husain bin Rooh:

يا محمد بن إبراهيم لان أخر من السماء فتخطفني الطير أو تهوى بي الريح في مكان سحيق أحب إلي من أن أقول في دين الله عز وجل برأيي أو من عند نفسي، بل ذلك عن الأصل ومسموع عن الحجة صلوات الله عليه وسلامه

Abu al-Qasim Husain bin Rooh the 3rd Safeer of the Imam has said,

"O Mohammad bin Ibrahim, To me, it's more beloved that I am thrown from the sky and then a bird snatches me or the wind takes me away than to say something about the religion of Allah by my opinion or from my own. But that (what I say) is from the source and what is heard from al-Hujjah (ع)."

(part of long narration quoted here)

[Source: Kamaal al-Deen, Ch. 45, H. 37]