Chat Completions

POST /v1/chat/completions is the OpenAI Chat Completions API. Use it when your code or SDK already speaks it. It reaches the same models, the same way, at the same prices as Open Responses.

Beta.

curl https://api.openagents.com/v1/chat/completions \
  -H "Authorization: Bearer $OPENAGENTS_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{"model": "openagents/fast",
       "messages": [{"role": "user", "content": "Hi"}]}'

What works the same

Chat Completions	Notes
system, developer, user, assistant, tool messages	As in OpenAI's API
Text and image_url parts
tools, tool_choice, parallel_tool_calls	Function tools
response_format	json_object and json_schema
max_tokens, max_completion_tokens	max_completion_tokens wins when both are set
reasoning_effort
temperature, top_p, stop, seed, user	Where the model supports them; otherwise ignored
stream, stream_options.include_usage	Usage arrives in the last chunk before [DONE]
finish_reason	stop, tool_calls, length, content_filter, or error
usage	Prompt, completion, cached, and reasoning tokens, plus our openagents cost object
openagents	The same routing options

What doesn't carry over

Feature	What happens
n above 1	400; send separate requests
input_audio parts, uploaded file_ids	400, naming the part
A message's name	Dropped
Reasoning	A summary arrives in a reasoning field; hidden reasoning can't be carried to the next turn
Citations and annotations	Dropped
Built-in tools such as web search	Function tools only
Several output items in one turn	Joined into one message, in order

When you need reasoning across turns or more than one output item, use Open Responses.