I can’t speak to trade agreements in an international sense, but there were certainly private agreements that modified conditions of trade between regions so as to increase the possibility of longer term trade. Here’s my best shot:
Mediterranean trade was already a big deal by CE 11th. Due to the diversity of resources spread around a relatively small body of water and its location along major trade routes between Asia and Western Europe, Mediterranean trade was a flourishing system that saw the rise of massively powerful families and polities alike; Venice and Florence rose to prominence through this trade, as did families like the Medici.^1 A massive part of this success depended on the use of agency systems, as goods were typically only sold after shipment and it was highly inefficient for a trader to follow his goods from place to place in order to sell them. Agency relations were simple and effectively resembled very basic trade agreements, but I'm going to dive a bit deeper and look at some of the traders that influenced the Venetians and Florentians, communities of "Greeks, Syrians, and jews that were so prominent in the conduct of long-distance trade in 1000".^2
I can't speak for Syrian and Greek groups, so I'll focus specifically on a prominent group of Jewish traders known today as the Maghribi. Though the Maghribi started out in the Abbasid caliphate (around Baghdad), they emigrated to North Africa in the second half of the tenth century and later on to areas like Spain, Sicily, Egypt, and even areas of eastern Europe.^3 When it came to long-distance trade among the general population, high asymmetric information enabled the common practice of principal-agent opportunism: agents could sell a merchant’s goods abroad, report total loss, and pocket the revenue themselves. There were courts in which merchants could make claims when they were cheated, but they moved exceedingly slowly and were “usually unable to verify agents’ claims and actions or to track down an agent who had emigrated”.^4 However, Jewish traders like the Maghribi were also subject to religious law and religious courts; while this did not directly enable their use of relatively complex trade agreements, it laid the ground for the establishment of a Maghribi trade coalition: in such a private organization, admittance was limited to trusted members of the Maghribi, and expulsion was the consequence of dishonest behavior.^5 As a result of such trust-based mechanisms, coalition traders were incentivized to cooperate to maximize their surplus: it is this incentivized cooperation that saw the rise of trade agreements like commenda, partnership, and formal friendships (among other variations). In commenda, one party provided capital while the other travelled and sold the goods, sharing profit or loss as specified by a sharing rule specified at the commenda’s establishment. Partnerships saw both partners investing capital and labor alike with a similar sharing rule in place. Formal friendships are more similar to trade agreements as we know them today: in such an agreement, traders operated in different areas but provided each other “with trade services in their respective trade centers”.^6 There was no monetary or emotional incentive; this agreement was typically organized as a means of expanding trade operations between regions. So as a whole, although I can’t say for sure whether exclusively governmental trade agreements were practiced in this era, private agreements certainly existed to discourage cheating, incentivize trade, and promote fair conditions of trade between prominent merchants.
I guess a simple 'yes' would have sufficed but there you go!
^1 Greif, Avner. "Reputation and Coalitions in Medieval Trade: Evidence on the Maghribi Traders." The Journal of Economic History 49, no. 04 (December 1989): 857-82. doi:10.1017/s0022050700009475, 871-872.
^2 Findlay, Ronald, and Kevin O'Rourke. Power and Plenty: Trade, War, and the World Economy in the Second Millenium. Vol. 6. Princeton, NJ: Princeton University Press, 2007, 109.
^3 Greif, Avner. “Reputation and Coalitions in Medieval Trade.” 861-862.
^4 Ibid, 866.
^5 Ibid.
^6 Ibid, 872.