I will first give a response to some of content of your question and then ask a question of my own:

you said: "it is an agglutinating language, a morpheme = a word."

short response: the term you are actually looking for is isolating

long response: agglutinating or agglutinative is one extreme in basic morphological typology. It does not, however, mean 1 morpheme =  1 word. Basic morphological typology has two axes:

• the axis of meanings per morpheme (agglutinative to fusional)
• the axis of morphemes per word. (isolating to polysynthetic)

Agglutinative is the extreme of the meanings/morpheme axis, where a single morpheme would carry only one unit of meaning (sememe), e.g. English /-s/ only conveys "plural". On the other extreme of the axis is fusional, where a single morpheme would carry multiple sememes, e.g. German /dem/ which conveys "definiteness, masculine gender, dative case".

Isolating, which is the term you were looking for to describe Mandarin, is the extreme end of the morphemes/word axis, meaning that words are composed of single syllables. On the other extreme of the axis is polysynthetic, where a single phonological word contains multiple morphemes. Good examples of such languages include Hawaiian, and most Bantu languages like Swahili and Sesotho. Most of the world's languages fall under the category of "synthetic" meaning words are comprised of a moderate number of morphemes.

you said: "its writing system is syllabic."

short response: - actually, Madarin uses a logographic writing system, unless you are referring to pinyin, which is an alphabet.

long response: - the world's writing systems can be organized into five categories based on correspondence between symbols and sounds:

• abjad systems have symbols to represent consonants, but not vowels. Examples include ancient Hebrew script and modern Arabic.
• alphabet systems have symbols to represent both consonants and vowels. Syllbles are built as a series of symbols. Examples include Latin script (English, French, Swahili, etc.), Greek, and Cyrillic (Russian)
• abugida systems have basic consonant symbols which are modified or take diacritics to indicate vowels. Examples include Ethiopic script (Amharic, Tigray), and Devenagari (Hindi).
• syllabary systems have a unique symbol for each unique syllable in the language (with some exceptions for codas). Examples include Katakana (Japanese), and Cherokee.
• logographic systems have little to no correspondence between sound and symbol. Instead, symbols abstractly represent words or morphemes. Examples include traditional Chinese script, ancient Egyptian hieroglyphics

Madarin traditionally uses a logographic script, which you can learn more about here: (http://www.omniglot.com/chinese/written.htm). Mandarin also sometimes uses a standardized alphabet called pinyin, which was developed in the Soviet Union in the 1930's. You can read more about pinyin here: (http://www.omniglot.com/chinese/mandarin_pts.htm)

you said: it is a tonal language, which means that tone plays an important role in creating new meanings.

short response: yes, but more specifically it means that tone can make the difference between two words.

long response: tone and intonation are words referring to the relative pitch (fundamental frequency) of an utterance. All languages have pitch, as it is impossible to produce sound without pitch. The question for linguistic typology, however, is which domain does tone impact in a given language.

• in intonational languages the domain of pitch is the utterance (i.e. pitch affects the overall meaning of a sentence). Thus in English we can affect the mood of a sentence by changing the pitch. If we raise the pitch at the end of an indicative utterance (a statement) it becomes an interrogative (a question). Or, we can add emphasis or emotion to our utterances through changing pitch.
• in tonal languages the domain of pitch is the word (i.e. pitch can make the difference between one word and another). Tonal languages vary greatly, and there are major differences between how tone works in American, Asian, and African languages. In isolating Asian languages, for example Mandarin, tone tends to be stable (it does not move or change). Thus each  morpheme/word has a certain pitch pattern (high, low, rising, falling) which always stays the same. If you change the pitch pattern on a syllable you change the word. Thus in Mandarin you can take the syllable "ma" and make four different words: mā "mother", má "hemp", mǎ "horse", and mà "scold".

Finally, I come to my question:

Can you be more specific about what you are looking for when you ask about the "distinct features" of Mandarin Chinese?

When you ask about "distinct features", I assume you are wanting to know how Mandarin contrasts with other languages, but this necessitates the question "Which languages?" What counts as distinct or not depends a lot on where your point of comparison is.

- Are you looking for a comparison between Mandarin and other Chinese languages?

- Are you looking for a comparison between Mandarin and English or other Indo-European languages?

- Are you looking for a typological description? Meaning, are you looking for what type of language Chinese compared to linguistic universals?

Similarly, when you ask about "features" are you asking about linguistic features or sociolinguistic or both?

- Are you looking for information on Mandarin sounds? Phonetics and phonology?

- Are you looking for information on Mandarin grammar? Morphology? Syntax? Discourse?

- Are you looking for information on the Chinese writing system?

- Are you looking for cultural or demographic information?

If you are able to answer this question, and its sub-questions I think you will receive an answer much more specific to your needs.

I will first give a response to some of content of your question and then ask a question of my own:

you said: "it is an agglutinating language, a morpheme = a word."

short response: the term you are actually looking for is isolating

long response: agglutinating or agglutinative is one extreme in basic morphological typology. It does not, however, mean 1 morpheme =  1 word. Basic morphological typology has two axes:

• the axis of meanings per morpheme (agglutinative to fusional)
• the axis of morphemes per word. (isolating to polysynthetic)

Agglutinative is the extreme of the meanings/morpheme axis, where a single morpheme would carry only one unit of meaning (sememe), e.g. English /-s/ only conveys "plural". On the other extreme of the axis is fusional, where a single morpheme would carry multiple sememes, e.g. German /dem/ which conveys "definiteness, masculine gender, dative case".

Isolating, which is the term you were looking for to describe Mandarin, is the extreme end of the morphemes/word axis, meaning that words are composed of single syllables. On the other extreme of the axis is polysynthetic, where a single phonological word contains multiple morphemes. Good examples of such languages include Hawaiian, and most Bantu languages like Swahili and Sesotho. Most of the world's languages fall under the category of "synthetic" meaning words are comprised of a moderate number of morphemes.

you said: "its writing system is syllabic."

short response: - actually, Madarin uses a logographic writing system, unless you are referring to pinyin, which is an alphabet.

long response: - the world's writing systems can be organized into five categories based on correspondence between symbols and sounds:

• abjad systems have symbols to represent consonants, but not vowels. Examples include ancient Hebrew script and modern Arabic.
• alphabet systems have symbols to represent both consonants and vowels. Syllbles are built as a series of symbols. Examples include Latin script (English, French, Swahili, etc.), Greek, and Cyrillic (Russian)
• abugida systems have basic consonant symbols which are modified or take diacritics to indicate vowels. Examples include Ethiopic script (Amharic, Tigray), and Devenagari (Hindi).
• syllabary systems have a unique symbol for each unique syllable in the language (with some exceptions for codas). Examples include Katakana (Japanese), and Cherokee.
• logographic systems have little to no correspondence between sound and symbol. Instead, symbols abstractly represent words or morphemes. Examples include traditional Chinese script, ancient Egyptian hieroglyphics

Madarin traditionally uses a logographic script, which you can learn more about here: (http://www.omniglot.com/chinese/written.htm). Mandarin also sometimes uses a standardized alphabet called pinyin, which was developed in the Soviet Union in the 1930's. You can read more about pinyin here: (http://www.omniglot.com/chinese/mandarin_pts.htm)

you said: it is a tonal language, which means that tone plays an important role in creating new meanings.

short response: yes, but more specifically it means that tone can make the difference between two words.

long response: tone and intonation are words referring to the relative pitch (fundamental frequency) of an utterance. All languages have pitch, as it is impossible to produce sound without pitch. The question for linguistic typology, however, is which domain does tone impact in a given language.

• in intonational languages the domain of pitch is the utterance (i.e. pitch affects the overall meaning of a sentence). Thus in English we can affect the mood of a sentence by changing the pitch. If we raise the pitch at the end of an indicative utterance (a statement) it becomes an interrogative (a question). Or, we can add emphasis or emotion to our utterances through changing pitch.
• in tonal languages the domain of pitch is the word (i.e. pitch can make the difference between one word and another). Tonal languages vary greatly, and there are major differences between how tone works in American, Asian, and African languages. In isolating Asian languages, for example Mandarin, tone tends to be stable (it does not move or change). Thus each  morpheme/word has a certain pitch pattern (high, low, rising, falling) which always stays the same. If you change the pitch pattern on a syllable you change the word. Thus in Mandarin you can take the syllable "ma" and make four different words: mā "mother", má "hemp", mǎ "horse", and mà "scold".

Finally, I come to my question:

Can you be more specific about what you are looking for when you ask about the "distinct features" of Mandarin Chinese?

When you ask about "distinct features", I assume you are wanting to know how Mandarin contrasts with other languages, but this necessitates the question "Which languages?" What counts as distinct or not depends a lot on where your point of comparison is.

- Are you looking for a comparison between Mandarin and other Chinese languages?

- Are you looking for a comparison between Mandarin and English or other Indo-European languages?

- Are you looking for a typological description? Meaning, are you looking for what type of language Chinese compared to linguistic universals?

Similarly, when you ask about "features" are you asking about linguistic features or sociolinguistic or both?

- Are you looking for information on Mandarin sounds? Phonetics and phonology?

- Are you looking for information on Mandarin grammar? Morphology? Syntax? Discourse?

- Are you looking for information on the Chinese writing system?

- Are you looking for cultural or demographic information?

If you are able to answer this question, and its sub-questions I think you will receive an answer much more specific to your needs.

Joshua makes some really good points. If you can be a bit ore specific about what you wish to compare with, you might get a lot more information.

I agree with Lian-Hee, Joshhua does give excellent comments regarding to your question. And here, I want to add a bit of my own idea as native speaker.

In Mandarin, tone always stays stable, except "一" (means one) and "不" (means no subjectively). The tone of those two words changes according to the tone of the word after them, without any change of meaning.

However, there are plenty words with more than one pronounciation, such as "好": (hǎo) means good, while (hào) means be fond of something, when each pronounciation corresponds to a different meaning and the meanings do not have to be related.

Unfortunately, in Mandarin many words share the same pronounciation. Taking the example Joshua used "ma", there are 9 "mā"s with totally different meanings, 8 "má"s, 15 "mǎ"s and 14 "mà"s.

As we can see, there is no correspondence between word and pronounciation in Mandarin. And it is sometimes confusing for people from other countries. When I explained to a spanish kid, old student of mine, that 蓝 (lán) of 蓝色 (blue) is not the same as 篮 (lán) of 篮球 (basketball), he asked me why Chinese people don't  give every word their own pronounciation. And I still remember the frustrated look of his.

As for Chinese grammar, I do recommend W. Klein's article. He explained it comparing to English and other Indo-European languages.

Mandarin is a little bit complicated when comprehending and expressing it, but we do have a pretty uncomplicated grammar. See? Here is the silver lining.

Article Aspect and Assertion in Mandarin Chinese

Not only "一" and "不", but also a third tone followed by another third tone changes into a second tone...

And I'm not even digging into the writing... which sometimes can be really funny, for we can see their culture in it.

So, I'd say there's plenty of distinctive features, when you compare it to English... it would really help if you could narrow the gap...

Hi Saide, I think this article may be able to answer all of your questions. It is by Michael Halliday, the key figure in systemic functional linguistics and himself a fluent Chinese speaker. It's better to look at how a genius linguist, native speaker of English who is so close to Chinese for many years talks about the characteristics of this language. 

https://functionallinguistics.springeropen.com/articles/10.1186/2196-419X-1-2

Many people have given you advaned linguistic and scientific answers.  Mine are very practical:

Mandarin does not use the English "to be" verb, giving Chinese learners of English great trouble.  

Mandarin also does not use articles such as A, AN, and THE, also giving Chinese speakers of English trouble.

Mandarin has VERY regular grammar, in contrast to western languages which often have very complex grammar.

Because Mandarin and western languages do not share a common heritage, many words do not translate precisely, i.e. these Chinese and English words have similar meaning, but are not exactly the same.  This makes literal and machine translation almost impossible.,

When i type tree in English, I have type t r e e,,,,,,,but in mandarin just click one character, that would be a tree. 

For me, what really makes mandarin different to the other languages I speak, is that ideas are expressed just but putting concepts one next to each other, without the need of conjugations or inflexions.

At the beginning it was really hard, because I always wanted to know whether a word was an adjective, a noun or a verb. Sometimes, it really doesn't matter. For instance, the sentence "我去学校" puts together the ideas of "me", "direction", and "school". Depending on the context, it could be imply different moments of time. Another example "我在这里" puts together "me", "static position", "near" and "place". It means "I am here", but does not exactly have a verb. With more complex sentences, this feature is stronger. the proverb "不怕慢，就怕站" is formed with the characters: "no", "fear", "slow", "eternity", "fear", "still". It can be translated by: "It is not important if you go slowly as soon as you don't remain still", or many other ways.