Important OpenAI Compatibility Limitations

API Behavior

Here are the most substantial differences from using OpenAI:
  • Multimodal input (images/audio) is not supported and will be ignored.
  • Prompt caching is not supported.
  • Most unsupported fields are silently ignored rather than producing errors. These are all documented below.

Detailed OpenAI Compatible API Support

Request Fields

Simple Fields

FieldSupport Status
modelUse “speed”
response_formatFully supported
streamFully supported
max_tokensIgnored
max_completion_tokensIgnored
stream_optionsIgnored
top_pIgnored
parallel_tool_callsIgnored
stopIgnored
temperatureIgnored
nIgnored
logprobsIgnored
metadataIgnored
predictionIgnored
presence_penaltyIgnored
frequency_penaltyIgnored
seedIgnored
service_tierIgnored
audioIgnored
logit_biasIgnored
storeIgnored
userIgnored
modalitiesIgnored
top_logprobsIgnored
reasoning_effortIgnored

Tools / Functions Fields

Tools are ignored.

Messages Array Fields

FieldSupport Status
messages[].roleFully supported
messages[].contentFully supported
messages[].nameFully supported
messages[].tool_callsIgnored
messages[].tool_call_idIgnored
messages[].function_callIgnored
messages[].audioIgnored
messages[].modalitiesIgnored

Response Fields

FieldSupport Status
idAlways empty
choices[]Will always have a length of 1
choices[].finish_reasonAlways empty
choices[].indexFully supported
choices[].message.roleFully supported
choices[].message.contentFully supported
choices[].message.tool_callsAlways empty
objectAlways empty
createdFully supported
modelAlways empty
finish_reasonAlways empty
contentFully supported
usage.completion_tokensAlways empty
usage.prompt_tokensAlways empty
usage.total_tokensAlways empty
usage.completion_tokens_detailsAlways empty
usage.prompt_tokens_detailsAlways empty
choices[].message.refusalAlways empty
choices[].message.audioAlways empty
logprobsAlways empty
service_tierAlways empty
system_fingerprintAlways empty

Error Message Compatibility

The compatibility layer maintains approximately the same error formats as the OpenAI API.

Header Compatibility

While the OpenAI SDK automatically manages headers, here is the complete list of headers supported by Parallel’s API for developers who need to work with them directly.
FieldSupport Status
authorizationFully supported
x-ratelimit-limit-requestsIgnored
x-ratelimit-limit-tokensIgnored
x-ratelimit-remaining-requestsIgnored
x-ratelimit-remaining-tokensIgnored
x-ratelimit-reset-requestsIgnored
x-ratelimit-reset-tokensIgnored
retry-afterIgnored
x-request-idIgnored
openai-versionIgnored
openai-processing-msIgnored