diff --git a/packages/backend/src/server/api/mastodon/endpoints/timeline.ts b/packages/backend/src/server/api/mastodon/endpoints/timeline.ts
new file mode 100644
index 0000000000..4d4cb2c419
--- /dev/null
+++ b/packages/backend/src/server/api/mastodon/endpoints/timeline.ts
@@ -0,0 +1,47 @@
+import { convertId, IdConvertType as IdType, convertAccount, convertConversation, convertList, convertStatus } from '../converters.js';
+import { ParsedUrlQuery } from "querystring";
+
+export function limitToInt(q: ParsedUrlQuery) {
+	let object: any = q;
+	if (q.limit)
+		if (typeof q.limit === "string") object.limit = parseInt(q.limit, 10);
+	if (q.offset)
+		if (typeof q.offset === "string") object.offset = parseInt(q.offset, 10);
+	return object;
+}
+
+export function argsToBools(q: ParsedUrlQuery) {
+	// Values taken from https://docs.joinmastodon.org/client/intro/#boolean
+	const toBoolean = (value: string) =>
+		!["0", "f", "F", "false", "FALSE", "off", "OFF"].includes(value);
+
+	// Keys taken from:
+	// - https://docs.joinmastodon.org/methods/accounts/#statuses
+	// - https://docs.joinmastodon.org/methods/timelines/#public
+	// - https://docs.joinmastodon.org/methods/timelines/#tag
+	let object: any = q;
+	if (q.only_media)
+		if (typeof q.only_media === "string")
+			object.only_media = toBoolean(q.only_media);
+	if (q.exclude_replies)
+		if (typeof q.exclude_replies === "string")
+			object.exclude_replies = toBoolean(q.exclude_replies);
+	if (q.exclude_reblogs)
+		if (typeof q.exclude_reblogs === "string")
+			object.exclude_reblogs = toBoolean(q.exclude_reblogs);
+	if (q.pinned)
+		if (typeof q.pinned === "string") object.pinned = toBoolean(q.pinned);
+	if (q.local)
+		if (typeof q.local === "string") object.local = toBoolean(q.local);
+	return q;
+}
+
+export function convertTimelinesArgsId(q: ParsedUrlQuery) {
+	if (typeof q.min_id === "string")
+		q.min_id = convertId(q.min_id, IdType.SharkeyId);
+	if (typeof q.max_id === "string")
+		q.max_id = convertId(q.max_id, IdType.SharkeyId);
+	if (typeof q.since_id === "string")
+		q.since_id = convertId(q.since_id, IdType.SharkeyId);
+	return q;
+}
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