Sasisho liko tayari.

Sasisho is the subject noun, liko is the part meaning is in this kind of sentence, and tayari means ready here.

So the basic structure is:

subject + is + ready

Because sasisho belongs to noun class 5 in Swahili, and class 5 uses the agreement marker li-.

The form -ko is used in this kind of present-state expression, so:

li- + -ko = liko

Swahili changes this form depending on the noun class. For example:

Chakula kiko tayari
Mtu yuko tayari
Masasisho yako tayari

Because ni is usually used for identification, like saying that one thing is another thing:

Hii ni simu = This is a phone

But for states or conditions such as ready, Swahili normally uses forms like iko, kiko, liko, yuko, depending on the noun class.

So Sasisho liko tayari is more natural than Sasisho ni tayari.

Sasisho is a class 5 singular noun.

That matters because Swahili nouns control agreement. The verb-like or copular part of the sentence has to match the noun class of the subject. Since sasisho is class 5 singular, the sentence uses li- in liko.

In this sentence, tayari means ready.

It does not change form to match noun class, so you do not get different versions of tayari for different nouns.

Yes, tayari can also mean already in other contexts, but here it clearly means ready because it is describing the state of sasisho.

There is a subject agreement marker inside it: li-.

It is not a separate pronoun like it in English, but it does show agreement with the subject noun. Swahili often does this even when the full noun is already stated.

So in Sasisho liko tayari, the noun sasisho appears openly, and li- in liko still agrees with it.

A natural plural is:

Masasisho yako tayari

Here, masasisho is the plural, and class 6 agreement is used, giving yako.

Because Swahili does not have articles like English the and a/an.

So sasisho can mean the update, an update, or just update, depending on the context.

Yes. Liko is enough to make this a complete sentence.

Swahili does not always need a separate word exactly like English to be. In sentences like this, the agreeing form liko does that job.

The normal, neutral order is:

Sasisho liko tayari

Other orders may be possible for emphasis in special contexts, but as a learner, this is the safest and most natural pattern to use.

A good pronunciation guide is:

sa-SI-sho LI-ko ta-YA-ri

Swahili usually stresses the second-to-last syllable of each word. Also, sh sounds like the sh in shoe.