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The Hicap API is a RESTful API compatible with the OpenAI API specification. Use it from any environment that supports HTTP requests, or through OpenAI’s official SDKs for Python, JavaScript/TypeScript, Go, and more.
Base URL: https://api.hicap.ai/v1

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Authentication

The Hicap API uses API keys for authentication. Create and manage your API keys in the Hicap Platform ↗.
Your API key is a secret. Do not share it or expose it in client-side code (browsers, mobile apps). Load API keys from environment variables or a secrets manager on the server side.
Provide your key via one of these headers: 
# Bearer authentication (OpenAI SDK default)
Authorization: Bearer YOUR-HICAP-API-KEY

# api-key header (Azure-style, also supported)
api-key: YOUR-HICAP-API-KEY

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Example request

curl https://api.hicap.ai/v1/chat/completions \
  -H "Authorization: Bearer $HICAP_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-5",
    "messages": [{"role": "user", "content": "Hello, world"}]
  }'

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Endpoints

All endpoints follow the OpenAI OpenAPI specification.

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Production

These endpoints are available on the production Hicap API (api.hicap.ai).

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Models

EndpointMethodDescription
/v1/modelsGETList model IDs available to your API key

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Chat Completions

EndpointMethodDescription
/v1/chat/completionsPOSTGenerate text, analyze images, call tools, stream responses
/v1/chat/completions/{completion_id}GETRetrieve a stored chat completion by ID
/v1/chat/completions/{completion_id}/messagesGETList messages from a stored chat completion

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Images

EndpointMethodDescription
/v1/images/generationsPOSTGenerate images from text prompts
/v1/images/editsPOSTEdit or extend existing images
/v1/images/variationsPOSTGenerate variations of an image

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Developer Preview

These endpoints are available on the Hicap developer API and are not yet in production.
Developer preview endpoints may change before general availability. Contact support@hicap.ai for access.

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Responses

EndpointMethodDescription
/v1/responsesPOSTCreate a model response (Responses API)
/v1/responses/{response_id}GET DELETERetrieve or delete a response
/v1/responses/{response_id}/cancelPOSTCancel an in-progress response
/v1/responses/{response_id}/input_itemsGETList input items for a response

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Realtime

EndpointMethodDescription
/v1/realtime/sessionsPOSTCreate a realtime session
/v1/realtime/transcription_sessionsPOSTCreate a transcription session

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Models

Pass any supported model ID in the model field. The Hicap API supports models across OpenAI, Anthropic, Google Gemini, Moonshot, Zhipu, and MiniMax — all through the same OpenAI-compatible interface. View all models →

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Streaming

Most text generation endpoints support server-sent events (SSE) for streaming responses. Set "stream": true in your request body to receive chunks as they are generated. 
curl https://api.hicap.ai/v1/chat/completions \
  -H "Authorization: Bearer $HICAP_API_KEY" \
  -H "Content-Type: application/json" \
  -d '{
    "model": "gpt-5",
    "messages": [{"role": "user", "content": "Write a haiku"}],
    "stream": true
  }'
Each SSE event contains a JSON chunk with incremental content. The stream ends with a [DONE] sentinel.

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Rate limits

Rate limits vary by plan and are applied per API key. When you exceed your limit, the API returns a 429 status code. Use exponential backoff to retry. The following rate limit headers are included in API responses:
HeaderDescription
x-ratelimit-limit-requestsMax requests allowed in the current window
x-ratelimit-limit-tokensMax tokens allowed in the current window
x-ratelimit-remaining-requestsRequests remaining in the current window
x-ratelimit-remaining-tokensTokens remaining in the current window
x-ratelimit-reset-requestsTime until the request limit resets
x-ratelimit-reset-tokensTime until the token limit resets
For higher limits, contact support@hicap.ai or upgrade your plan in the Hicap Platform ↗.

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Errors

The Hicap API uses standard HTTP status codes and returns JSON error bodies.
StatusTypeDescription
400invalid_request_errorMalformed request body or missing required fields
401authentication_errorInvalid or missing API key
403permission_errorAPI key lacks required permissions
404not_found_errorRequested resource does not exist
429rate_limit_errorRate limit exceeded — back off and retry
500api_errorInternal server error — retry with exponential backoff
503overloaded_errorServer temporarily overloaded — retry after a short delay
Error responses include a JSON body: 
{
  "error": {
    "message": "Invalid API key provided",
    "type": "authentication_error",
    "code": "invalid_api_key"
  }
}

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Request IDs

Every API response includes an x-request-id header with a unique identifier for that request. Log this value in production — it allows the Hicap support team to quickly locate and diagnose issues if you need help.

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Versioning

The Hicap API follows the OpenAI v1 API specification. We are committed to maintaining backward compatibility within the v1 API and will avoid breaking changes whenever possible.