Documenting REST APIs

DOCUMENTING REST APIS
BY TOM JOHNSON
IDRATHERBEWRITING.COM
STC Summit 2015  Columbus, Ohio  @tomjohnson

CONVENTIONS
• Access the course module at
http://idratherberwriting.com/restapicourse
• 1.1 Numbers in slide headings refers to the place in the
course module.
•  This icon indicates an activity you’re supposed to do.
• If you get lost, read the course page.

1.0 OVERVIEW
• Focus of the course is REST APIs
• Time to completion
• Learn with a real example and context
• No programming skills required

1.0 OVERVIEW
What you’ll need:
• Text editor
• Chrome browser
• Postman REST Client
• cURL
• Network connection
Follow along online:
idratherbewriting.com/restapicourse

1.1 INTRODUCTION TO REST
API DOCUMENTATION
Complete and
accurate docs are
most important factor
in APIs

API DOCUMENTATION
REST APIs are
taking off in a
huge way

API DOCUMENTATION
Job market is hot for
API technical writers

API DOCUMENTATION
API doc is a new
world for most tech
writers

API DOCUMENTATION
Increasing learning
materials about API
documentation

1.2 USING A REST API LIKE A
DEVELOPER
An API is an interface
between systems.

DEVELOPER
Our course scenario:
Weather forecast API

DEVELOPER
 Get an idea of the
end goal

DEVELOPER
 Browse the
available APIs on
Mashape

DEVELOPER
Find the
"Weather" API by
fyhao

DEVELOPER
 Answer some questions about the API
• What does the API do?
• How many endpoints does the API have?
• What does each endpoint do?
• What kind of parameters does each endpoint take?
• What kind of response does the endpoint provide?
✔ Terminology tip: API == Endpoint

1.3 GET THE
AUTHORIZATION KEYS
• Authorization for making API calls
• License access to the API
• Rate limit the number of requests
• Control availability of certain features within
the API

1.3 GET THE
AUTHORIZATION KEYS
 Get the
Mashape
authorization keys

1.3 GET THE
AUTHORIZATION KEYS
 To get the keys:
1. Click Sign Up Free and create an account.
2. Click Applications on the top nav bar.
3. Click Get the Key.
4. In the dialog box, click Copy. (Choose the Testing
keys.)
5. Open up a text editor and paste the key.

1.3 GET THE
AUTHORIZATION KEYS
Text editors:
• Sublime Text (Mac or PC)
• TextWrangler (Mac)
• WebStorm (Mac or PC)
• Notepad++ (PC)

1.4 MAKE A CURL CALL
 Prepare the cURL call:
1. Go into Weather API.
2. Copy the cURL request example for the aqi
endpoint into your text editor.
3. Important: If you're on Windows, change the single
quotes to double, and add -k as well to work around
security certificate issues.
4. Swap in your own API key.
5. Use Google Maps to find the latitude and longtitude
of your current location.

 Make the call in cURL (Mac)
1. Open a terminal.
2. Paste the call you have in your text editor into the
command line.
3. Press your Enter key.

 Make the call in cURL (Windows)
1. Copy the cURL call from your text editor.
2. Go to Start and type cmd to open up the command
line.
3. Right-click and then select Paste to insert the call.

If it didn’t work, try the Advanced REST Client

• cURL is a cross-platform way to show requests and
responses
• REST APIs follow the same request/return model of the
web
•  Try using cURL to GET a web page:
curl http://example.com
1.5 UNDERSTANDING CURL

Requests and responses include headers too
 Use –i or -I include the response header:
curl http://example.com -i
curl http://example.com -I

Other methods you can use besides GET:
• POST: Create a resource
• GET: Read a resource
• PUT: Update a resource
• DELETE: Delete a resource

Specifying the method with a cURL call
--get
-X GET
-x PUT
curl –X GET http://example.com

Passing headers into the request:
-H
curl --get --include 'https://simple-
weather.p.mashape.com/aqi?lat=37.354108&lng=
-121.955236’
-H 'X-Mashape-Key:
WOyzMuE8c9mshcofZaBke3kw7lMtp1HjVGAjsndqIPbU
9n2eET'
-H 'Accept: text/plain'

Passing data into the request:
-d
curl -i -H "Accept: application/json" -X
POST -d "{status:MIA}"
http://personsreport.com?status

Make cURL more readable:
curl -i
-H "Accept: application/json"
-X POST
-d "{status:MIA}"
http://personsreport.com?status

Query strings:
?lat=37.354108&lng=-121.955236
Listening multiple parameters:
&parameter1&parameter2&parameter3

1.6 SUBMIT REST CALLS
THROUGH POSTMAN
GUI clients make REST calls a little easier
Common GUI clients:
• Postman
• Advanced REST Client
• Paw

THROUGH POSTMAN
 Insert the cURL
call into Postman
following the
sample screenshot

THROUGH POSTMAN
 View the format of the weatherdata response in pretty
JSON

1.7 ANALYZE THE JSON
RESPONSE
Prettify the JSON response:
http://jsonformatter.curiousconcept.com/
JSON is how most REST APIs structure the response

RESPONSE
JSON objects are key-value pairs:
{
"key1":"value1",
"key2":"value2"
}
JSON objects start and end with curly braces { }.

RESPONSE
JSON arrays are lists of items:
["first", "second", "third"]
Arrays start and end with square brackets [ ].

RESPONSE
An array can contain a list of objects:
[
{
"name":"Tom",
"age":39
},
{
"name":"Shannon",
"age":37
}
]

RESPONSE
An object can contain arrays:
children: ["Avery","Callie","lucy","Molly"],
hobbies:
["swimming","biking","drawing","horseplaying
"]

RESPONSE
 Identify the objects and arrays in the weatherdata API
response.
• Where are the objects?
• Where are the arrays?

1.8 LOG THE JSON
RESPONSE TO THE CONSOLE
Making use of the JSON response
 Use the sample code from Mashape to parse and
display the REST response:
http://docs.mashape.com/javascript

1.8 LOG THE JSON
 Customize the Mashape code with the weatherdata
endpoint:
1. Open text editor. Insert Mashape code.
2. Customize the url to the useweatherdata endpoint.
3. Enter your API key.
4. Uncomment out the next to console.log(data).
5. Save and view the file in Chrome.
6. Open the Developer Console: View > Developer >
JavaScript Console. Refresh page.

1.8 LOG THE JSON
 You can customize your Console log messages
 Inspect the payload
 Replace "undefined”:
document.getElementById("output").innerHTML
=
data.query.results.channel.item.description;

1.9 ACCESS THE VALUES
FROM JSON
Dot notation allows you to access specific values from the
JSON response
data.query.results.channel.item.description

FROM JSON
How dot notation works
"data": {
"name": "Tom"
}
To access Tom, I would use data.name.

FROM JSON
Use square brackets to access the values in an array:
"data" : {
"items": ["ball", "bat", "glove"]
}
To access glove, you would use data.items[2]

FROM JSON
 Download the dotnotationexercise.html file from the
workshop files.
 Change john.children[0].child1 to display the
following:
• green
• nike
• goldenrod
• Sarah

FROM JSON
 Get the wind speed from the weather API weatherdata
endpoint.
 Download the windcalls.html file from the workshop files.
Look at the different values accessed from the JSON
response.

2.0 YOU HAVE A NEW API TO
DOCUMENT
Shift perspectives: Now you're the technical writer
You have a new endpoint to document
 Review the wiki page:
http://idratherbewriting.com/restapicourse2-0/

DOCUMENT
Essential sections in REST API documentation:
• Resource description
• Endpoint
• Methods
• Parameters
• Request submission example
• Request response example
• Status and error codes
• Code samples

DOCUMENT
 Create the basic structure for the endpoint
documentation
 Use a text editor to create the sections.
Bonus: Use Markdown syntax.

2.1 DOCUMENTING THE
RESOURCE DESCRIPTION
The terminology to describe a "resource" varies:
• API calls
• Endpoints
• API methods
• Calls
• Resources
• Objects
• Services
• Requests

2.1 DOCUMENTING THE
 Look at some examples:
• Mailchimp
• Twitter
• Instagram

2.1 DOCUMENTING THE
Referring to resources by the endpoint name can get
problematic:
api_site.com/{apikey}/users
// gets all users
api_site.com/{apikey}/users/{userId}
// gets a specific user
api_site.com/{apikey}/rewards
// gets all rewards
api_site.com/{apikey}/rewards/{rewardId}
// gets a specific reward
api_site.com/{apikey}/users/{userId}/rewards
// gets all rewards for a specific user
api_site.com/{apikey}/users/{userId}/rewards/{rewardId}
// gets a specific reward for a specific user
api_site.com/{apikey}/users/{userId}/rewards/{missionId}
// gets the rewards for a specfic mission related to a specific user
api_site.com/{apikey}/missions/{missionid}/rewards
// gets the rewards available for a specific mission

2.1 DOCUMENTING THE
One resource can
have multiple
endpoints

2.1 DOCUMENTING THE
When describing the resource, start with a verb.
 Review some examples:
• Delicious API
• Foursquare API
• Box API

2.1 DOCUMENTING THE
 Review the surf report wiki page (2.0) containing the
information about the endpoint, and try to describe the
endpoint in the length of one or two sentences.

2.1 DOCUMENTING THE
•  Critique the Mashape Weather API descriptions
• There’s a difference between reference docs versus user
guides
• Re-using the resource description

2.2 DOCUMENTING THE
ENDPOINT DEF. AND METHOD
Terminology for the endpoint definition varies:
• Requests
• Endpoints
• API methods
• Resource URIs
• Resource URLs
• URLs
• URL syntax

2.2 DOCUMENTING THE
The endpoint definition usually contains the end path only
/surfreport/{beachId}
Represent parameter values with curly braces

2.2 DOCUMENTING THE
You can list the
method beside the
endpoint

2.2 DOCUMENTING THE
•  Write the endpoint definition for surfreport
• Aim for 1-3 sentences

2.3 DOCUMENTING
PARAMETERS
Parameters are
ways to configure
the endpoint

2.3 DOCUMENTING
PARAMETERS
Data types indicate the format for the values:
• String
• Integer
• boolean

2.3 DOCUMENTING
PARAMETERS
• Parameter order doesn’t matter
/surfreport/{beachID}?days=3&units=metric&ti
me=1400
• Note any max and min values
• Note whether parameters are optional or required

2.3 DOCUMENTING
PARAMETERS
• You can also pass parameters in the JSON body
{
"days": 2,
"units": "imperial",
"time": 1433524597
}
• Time values usually follow ISO or Unix format

2.3 DOCUMENTING
PARAMETERS
 Construct a table to list the surfreport parameters

2.4 DOCUMENTING SAMPLE
REQUESTS
The sample request clarifies how to use the endpoint
http://api.nytimes.com/svc/search/v2/article
search.response-format?[q=search
term&fq=filter-field:(filter-
term)&additional-params=values]&api-key=####

REQUESTS
API Explorers
provide interactivity
with your own data

REQUESTS
API Explorers can be
dangerous in the hands of
a newbie

REQUESTS
• If different requests return different responses, show
multiple responses
 Document the sample request with the
surfreport/{beachId} endpoint

RESPONSES
• Provide a sample response for the endpoint
• Example from Flattr API
• Define what the values mean in the endpoint response

RESPONSES
Strategies for documenting nested objects
 Check out the following approaches:
• Dropbox
• Bit.ly
• eBay

RESPONSES
Information design choice: Where to include the
response

RESPONSES
• Use realistic values in the response
• Format the JSON in a readable way
• Add syntax highlighting
• Some APIs embed dynamic responses

RESPONSES
 Create a section for a sample request in your
surfreport/{beachId} endpoint

2.6 DOCUMENTING RESPONSE
AND ERROR CODES
• Response codes let you know the status of the request
• Common status codes follow standard protocols:
http://www.restapitutorial.com/httpstatuscodes.html

AND ERROR CODES
• List the HTTP
response and error
codes
• Main page and also on
each endpoint where
relevant

AND ERROR CODES
 Run your request and look at your header code
 List three status codes for surfreport/{beachId}

2.7 DOCUMENTING CODE
SAMPLES IN REST APIS
• Code samples bridge the gap between reference and
user guides
•  Look at the code sample on Mashape:
http://docs.mashape.com/javascript
• Code samples are like candy for developers

• You are not the audience
• Focus on the why, not the what
• Focus on the why, not the what
• Focus your explanation on your company's code only

• Keep code samples simple
• Add both code comments and before-and-after
explanations
• Make code samples copy-and-pastable

Provide a code sample in your target language

• From code samples to real tasks in user guides
•  Your turn to practice: Create a code sample and
documentation for the surfreport endpoint

2.8 PUTTING IT ALL
TOGETHER
• View my sample here:
http://idratherbewriting.com/restapicourse2-8/
• Share and comment on each other’s samples?

2.9 CREATING THE USER
GUIDE
User guides versus reference documentation
Essential sections in a user guide:
• Overview
• Getting started
• Authorization keys
• Core concepts
• Rate limits
• Code samples
• Hello world tutorial
• Quick reference
• Glossary

GUIDE
Overview
section

GUIDE
Getting started
section

GUIDE
Authorization keys

GUIDE
Rate limits

GUIDE
Quick reference
guide

3.0 COMPLETION
Learning summary
• How to make calls to an API using cURL and Postman
• How to pass parameters to API calls
• How to inspect the objects in the JSON payload
• How to use dot notation to access the JSON values you
want
• How to display the integrate the information into your site

3.0 COMPLETION
Learning summary
• Documenting the resource description
• Documenting the endpoint definition and method
• Documenting parameters
• Documenting the request example
• Documenting the response example
• Providing a code example
• Listing status codes

THANKS!
Tom Johnson
idratherbewriting.com
tomjohnson1492@gmail.com

IMAGE CREDITS
Most images are screenshots linked to a webpage, but some
are from Flickr. Required attribution is as follows:
• Structure, https://flic.kr/p/oFD6MM Rafal Zych
• Earth patterns. https://flic.kr/p/ssQqiL Evriel Venefice
• Dave’s Bike Tools, https://flic.kr/p/QMVMw Bri Pettis

Documenting REST APIs

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