Chat Completions API

Use different sources for different questionsUse the Apifox API reference for full field and response schemas. Use the Model Marketplace and the capability matrix for current model availability, token-group access, and protocol selection.

curl 'https://nexusapi.link/v1/chat/completions' \ -H 'Content-Type: application/json' \ -H 'Authorization: Bearer YOUR_API_KEY' \ -d '{ "model": "YOUR_MODEL_ID", "messages": [ {"role": "user", "content": "Hello"} ] }'

Header	Required	Value
`Content-Type`	Yes	`application/json`
`Authorization`	Yes	`Bearer YOUR_API_KEY`

Header

Required

Value

Content-Type

Yes

application/json

Authorization

Yes

Bearer YOUR_API_KEY

Common failures

Result	First things to check
401	Missing, invalid, expired, or disabled API key.
429	Request rate, concurrency, or temporary upstream throttling.
500 / 502 / 503	A temporary processing or upstream failure.
524	The request exceeded a waiting limit.

If you see status_code=500, not implemented while calling a current Anthropic-type Claude channel through /v1/responses, do not retry it as a normal 500. Use /v1/chat/completions for a custom OpenAI-style application, or use Claude Code’s native Messages configuration.

For any other error, keep the Request ID and use the self-check guide. Avoid rapid retries.

Get started

Models and billing

Client tools

Troubleshooting

Developer API

Endpoint

Minimal request

Required headers

Common failures

​Endpoint

​Minimal request

​Required headers

​Common failures

Endpoint

Minimal request

Required headers

Common failures