The book on the Macedonian Wars belongs to the less preserved parts, but fortunately, we have access to Appian's sources Polybius or Livy.
The translation was made by Horace White; notes by Jona Lendering.
The Second Macedonian War (Cont'd)
 [From Constantine Porphyrogenitus, The Embassies] Flamininus replied, "Alexander cannot be ignorant of the custom of the Romans, who never destroy an enemy at once, but have spared many offenders, as recently the Carthaginians, restoring their property to them and making allies of those who had done them wrong. You forget also that there are many barbarous tribes on the border of Macedonia, who would make easy incursions into Greece if the Macedonian kings were taken away. Wherefore, I think that the Macedonian government should be left to protect you against the barbarians, but Philip must retire from those Greek places that he has hitherto refused to give up, and must pay the Romans 200 talents for the expenses of the war, and give hostages of the most noble families, including his own son, Demetrius. Until the Senate ratifies these conditions there shall be an armistice of four months."
 [From Constantine Porphyrogenitus, The Embassies] Philip accepted all these conditions,note[196 BCE.] and the Senate, when it learned the facts, ratified the peace, but considered the terms granted by Flamininus too lenient, and, accordingly, decreed that all the Greek cities that had been under Philip's rule should be free, and that he should withdraw his garrisons from them before the next celebration of the Isthmian games; that he should deliver to Flamininus all his ships, except one with six benches of oars and five small ones with decks; that he should pay the Romans 500 talents of silver down, and remit to Rome 500 more in ten years, in annual installments; and that he should surrender all prisoners and deserters in his hands. These conditions were added by the Senate and Philip accepted them all, by which it was made plain that those named by Flamininus were much too lenient. They sent to him as counselors ten men (as was customary at the end of a war), with whose aid he should regulate the new acquisitions.
 [From Constantine Porphyrogenitus, The Embassies] When he had arranged these things with them he went to the Isthmian games, and, the stadium being full of people, he commanded silence by trumpet and directed the herald to make this proclamation, "The Roman people and Senate, and Flamininus, their general, having vanquished the Macedonians and Philip, their king, order that Greece shall be free from foreign garrisons, not subject to tribute, and shall live under her own customs and laws."
Thereupon there was great shouting and rejoicing and a scene of rapturous tumult; and groups here and there called the herald back in order that he might repeat his words for them. They threw crowns and fillets upon the general and voted statues for him in their cities. They sent ambassadors with golden crowns to the Capitol at Rome to express their gratitude, and inscribed themselves as allies of the Roman people. Such was the end of the second war between the Romans and Philip.
 [From Constantine Porphyrogenitus, The Embassies] Not long afterwardnote[In 190 BCE.] Philip lent aid in Greece to the Romans in their war against king Antiochus. As they were moving against Antiochus in Asia, passing through Thrace and Macedonia by a difficult road, he escorted them with his own troops, supplied them with food and money, repaired the roads, bridged the unfordable streams, and dispersed the hostile Thracians, until he had conducted them to the Hellespont.note[This subject matter is also treated by Appian in the Syrian War §23.] In return for these favors the Senate released his son Demetrius, who had been held by them as a hostage, and remitted the payments of money still due from him. But these Thracians fell upon the Romans when they were returning from their victory over Antiochus, when Philip was no longer with them, carried off booty and killed many - by which it was plainly shown how great a service Philip had rendered them when they were going.
 [From Constantine Porphyrogenitus, The Embassies] That war being ended, many of the Greeks charged Philip with doing or omitting various things,note[183 BCE.] in disregard of the orders given by Flamininus when he settled the affairs of Greece. To answer these charges Demetrius went as an envoy to Rome on his father's behalf, the Romans being well pleased with him aforetime, when he had been a hostage, and Flamininus strongly recommending him to the Senate. As he was a very young man and somewhat flustered, they directed him to read his father's memorandum in which were written down, one by one, the things already done and those yet to be done, although decided upon contrary to justice; for, indeed, his unjust acts were prominent in the thought of many.
Nevertheless, the Senate, having regard to his late zeal in the matter of Antiochus, said that it would pardon him, but added that it did so on account of Demetrius. Philip, having been confessedly most useful to them in the war with Antiochus, when he might have done them the greatest damage if he had cooperated with Antiochus, as the latter asked him to, expecting much on this account and now seeing himself discredited and accused, and considered worthy of pardon rather than of gratitude, and even this merely on account of Demetrius, was indignant and angry, but concealed his feelings for a time. Afterwards, in a certain arbitration before the Romans, they transferred much of his territory to Eumenes, seeking all the time to weaken him. Then, at once, he began secretly preparing for war.