This 200-901 practice question tests your understanding of understanding and using apis. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A developer is using the Cisco Webex Teams API to create a room and add members. The API returns a 400 error. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Invalid access token
Why wrong: Invalid token would result in a 401 Unauthorized.
Missing required fields
400 errors are commonly due to missing or invalid fields.
Network connectivity issue
Why wrong: Network issues typically result in timeout or connection errors, not a 400 response.
Room name already exists
Why wrong: Duplicate names might cause a 409 Conflict, not 400.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Missing required fields
A 400 Bad Request error from the Cisco Webex Teams API indicates that the server cannot process the request due to a client-side error, most commonly missing required fields in the request body. When creating a room, the API requires a 'title' field; omitting it or sending an empty value triggers a 400 response. This is distinct from authentication or network issues, which produce different HTTP status codes.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Invalid access token
Why it's wrong here
Invalid token would result in a 401 Unauthorized.
Missing required fields
Why this is correct
400 errors are commonly due to missing or invalid fields.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Network connectivity issue
Why it's wrong here
Network issues typically result in timeout or connection errors, not a 400 response.
Room name already exists
Why it's wrong here
Duplicate names might cause a 409 Conflict, not 400.
Common exam traps
Cisco often tests the distinction between HTTP 4xx status codes, leading candidates to confuse authentication errors (401) with client-side request errors (400) when the actual issue is missing or malformed data.
Detailed technical explanation
The Webex Teams REST API uses standard HTTP status codes to indicate success or failure. A 400 error specifically maps to a malformed request syntax, invalid request message framing, or deceptive request routing (RFC 7231 Section 6.5.1). In practice, the API validates required JSON fields like 'title' for room creation; if absent, the server rejects the request before any business logic (e.g., duplicate name checks) is executed. This behavior is consistent with many RESTful APIs that enforce strict schema validation at the endpoint level.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A practitioner preparing for the 200-901 exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
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FAQ
Understanding and Using APIs — This question tests Understanding and Using APIs — Read the scenario before looking for a memorised answer..
The correct answer is: Missing required fields — A 400 Bad Request error from the Cisco Webex Teams API indicates that the server cannot process the request due to a client-side error, most commonly missing required fields in the request body. When creating a room, the API requires a 'title' field; omitting it or sending an empty value triggers a 400 response. This is distinct from authentication or network issues, which produce different HTTP status codes.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
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