"supplementary agreements" is correct and commonly used in written English
It refers to additional agreements that are made in addition to a main agreement. Example: The two companies signed a main contract outlining the terms of their partnership, but they also made several supplementary agreements to cover specific details that were not included in the main contract.
For ease of use, the otherwise not easily accessible annexes and protocols, where relevant, and the supplementary agreements are printed.
The original agreement adopted in 1875 applied only to letter mail; other postal services, such as parcel post and international money orders, have been regulated by supplementary agreements that are binding only on signing members.
European diplomats have been meeting with their U.S. counterparts to try to negotiate supplementary agreements to address Trump's concerns, including the absence of mechanisms to address Iran's missile programs and its support for militant groups in the Middle East.
The supplementary agreement in regard to naval or coaling stations signed between the two Governments on July 2, 1903, also shall continue in effect in the same form and on the same conditions with respect to the naval station at Guantanamo.
The tasks and procedures of the two EEA bodies European Surveillance Authority and EFTA Court, which are used for monitoring and dispute resolution, are explained by commenting on the EEA Regulations and the supplementary agreement concluded between Norway, Iceland and Liechtenstein.
A supplementary agreement signed today talks of Cuba, whose reserves of hard currency are limited, exporting vaccines and sugar technology to Venezuela, along with doctors and up to 3,000 physical education teachers and sports coaches and trainers, who might be unemployed if they remained in Cuba.
Instead, the EU will have to decide whether to pursue its proposals, originally concocted to persuade Trump to stay in the deal, to negotiate a supplementary agreement with Iran covering its ballistic missile program, its foreign policy interventionism in the Middle East and the controversial sunset clauses in the deal.
The question of digital DNA arose throughout years of negotiations leading up to the Nagoya Protocol, a supplementary agreement to the broader United Nations Convention on Biological Diversity (CBD).
The rights, privileges, and obligations of the foreign forces and their members stationed in Germany were then based on the Bonn forces convention, the forerunner of the North Atlantic Treaty Organization Status of Forces Agreement (NATO SOFA) and the supplementary agreement that followed.
Protocol of the Supplementary Agreement to the Convention between the Government of the Union of Soviet Socialist Republics and the Imperial Government of Iran on pest control.
While Syngenta was grappling with its botched shipments, the 119 signatories of the United Nations Cartagena Protocol on Biosafety (a supplementary agreement of the Convention on Biological Diversity) were deciding whether to create documentation requirements for bulk shipping of "living modified organisms," which are the live GM organisms such as seeds (rather than milled forms such as flour).
