How to Create a Multi-tag URI Request to /questions

Question

Just want to confirm if I'm doing this right. The /questions guide doesn't mention this.

Let's say I want to ask for multiple tags in one request, am I doing this right?

https://api.stackexchange.com/2.2/questions?pagesize=70&order=desc&sort=activity&site=stackoverflow&tagged=google-docs-api&tagged=firebase-database&tagged=android-sdk&tagged=google-drive-sdk&fromdate=1515888000 

So basically what I'm doing is to chain multiple 'tagged=ACTUAL_TAG' together. I get a successful response but when I compare that in the "Stack Overflow search q" results,

https://stackoverflow.com/search?q= 

I get varying results/responses - they're not exactly alike. Some of the questions from the "Stack Overflow search q" are not found in my URI request. That's why I'm asking if I'm doing something wrong..

EDIT: As answered below, the /search URI request did the trick for me as it allows "OR" tags where you chain tags together.

Answer 1

From the /questions doc:

...use the tagged parameter with a semi-colon delimited list of tags. This is an and contraint(sic), passing tagged=c;java will return only those questions with both tags...

^{(Emphasis added)}

If you want questions that have either tag, use the /search route (or /search/advanced).

For example:
/2.2/search?tagged=google-docs-api;firebase-database;android-sdk;google-drive-sdk...

As for why the API sometimes differs from the website search, that has been asked a few times both here and elsewhere. EG, see Why is there a difference between "questions" and "search" in API?.

But a common reason for API calls that use dates (fromdate etc.) to return unexpected results is not taking into account how the API handles unix epoch time.