Send message (OpenAI format).

post

https://app.customgpt.ai/api/v1/projects/{projectId}/chat/completions

Sends a message using the OpenAI-compatible request and response format. Use this if you are migrating from OpenAI or want to use existing OpenAI client libraries. Supports streaming for real-time responses.

Notes: This is a convenience endpoint for OpenAI compatibility. For full CustomGPT features, use the native message endpoint.

Recent Requests

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Path Params

projectId

integer

required

The unique identifier of the agent to send the message to.

Body Params

Send a message in OpenAI chat completion format.

messages

array of objects

The messages to send to the agent

messages

model

string | null

ID of the model to use

stream

boolean

Defaults to false

Whether to stream the response

lang

string

Defaults to en

Response language

external_id

string | null

External identifier

is_inline_citation

boolean

Defaults to false

Whether to include inline citations

labels

array | null

Optional source-label filter. Accepts two formats: (1) Flat array of label IDs or names for OR semantics, e.g. ["A","B","C"]. (2) Array of arrays for AND/OR logic (inner=OR, outer=AND), e.g. [["A","B"],["C","D"]] means (A OR B) AND (C OR D). Max 20 groups, 50 labels per group, 500 total. Invalid values are ignored.

labels

labels_exclusive

boolean

Defaults to false

If true, search only pages with provided labels. If false, search pages with provided labels plus unlabeled pages.

Headers

string

enum

Defaults to application/json

Generated from available response content types

Allowed:

Responses

200

OpenAI-compatible chat completion response.

Non-streaming (stream: false or omitted): Returns a single JSON object with the complete response.

Streaming (stream: true): Returns Server-Sent Events (SSE) with text/event-stream content type.

Each SSE event is prefixed with data: followed by a JSON object:

data: {"id":"chatcmpl-abc123","object":"chat.completion.chunk","created":1743037634,"model":"gpt-4","choices":[{"index":0,"delta":{"content":"Hello"},"finish_reason":null}]}

The stream ends with:

data: [DONE]

Key fields per chunk:

id: unique completion ID
object: always chat.completion.chunk
created: Unix timestamp
choices[0].delta.content: incremental text fragment
choices[0].finish_reason: null during stream, stop on final chunk

JavaScript client example:

const response = await fetch(
  'https://app.customgpt.ai/api/v1/projects/{projectId}/chat/completions',
  {
    method: 'POST',
    headers: {
      'Authorization': 'Bearer YOUR_API_KEY',
      'Content-Type': 'application/json'
    },
    body: JSON.stringify({
      messages: [{ role: 'user', content: 'Hello' }],
      stream: true
    })
  }
);

const reader = response.body.getReader();
const decoder = new TextDecoder();

while (true) {
  const { done, value } = await reader.read();
  if (done) break;

  const lines = decoder.decode(value).split('\n');
  for (const line of lines) {
    if (!line.startsWith('data: ')) continue;
    const payload = line.slice(6);
    if (payload === '[DONE]') break;

    const chunk = JSON.parse(payload);
    const text = chunk.choices[0]?.delta?.content || '';
    process.stdout.write(text);
  }
}

Language

Credentials

Bearer

JWT

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Response

Click Try It! to start a request and see the response here! Or choose an example:

application/json

text/event-stream

400Bad Argument

401API Token is either missing or invalid

404Agent not found

429Resource Exhausted when sending a message to a conversation

500Internal Server Error

501Unsupported Argument