The phrase "agreed to observe" is correct and usable in written English.
It can be used when indicating that someone has consented to follow or adhere to certain rules, guidelines, or practices.
Example: "The parties involved have agreed to observe the terms outlined in the contract."
Alternatives: "consented to follow" or "committed to adhere".
Pomahac agreed to observe the procedure, to see how he could be unobtrusive.
On that occasion, the British media had been aware of the deployment but agreed to observe a strict media blackout.
In Thursday morning's session the two teams agreed to observe a minute's silence to remember the victims of "terrorism" – but quickly blamed each other for perpetrating the violence.
The Palestinians have suspended their intifada: most of the armed factions have agreed to observe a truce, though they call it merely a tahdia, or "lull".
The mortar fire interrupted a ceasefire called for by the UN on humanitarian grounds, which both Israel and Hamas had agreed to observe between 0700 GMT and 1200 GMT.
Later that month the Chinese signed the Beijing Convention, in which they agreed to observe the treaties of Tianjin and also ceded to the British the southern portion of the Kowloon Peninsula adjacent to Hong Kong.
What's more, they got Google, Microsoft, Yahoo and AOL to agree to observe them.
But China has refused to join the MRC or to agree to observe its resource management guidelines, preferring to remain a "dialogue partner".
It may still be useful for groups of governments (like the Council of Europe) to band together to agree to observe certain standards.
Mayor Dickinson said that he admired Dr. King and his achievements, but that he would not agree to observe the holiday unless the labor unions that represent town workers first agreed to give up one of their other paid holidays.
The researchers only observed bai jiu makers and sellers who agreed to be observed.
