nicottone
01/13/2026, 4:55 PMAI Evy
01/13/2026, 4:55 PMAI Evy
01/13/2026, 4:56 PMPATCH /update-retell-llm/{llm_id} endpoint to update the general_prompt field.
Here's an example using the JavaScript SDK:
javascript
import Retell from 'retell-sdk';
const client = new Retell({
apiKey: 'YOUR_RETELL_API_KEY',
}) ;
const llmResponse = await client.llm.update('16b980523634a6dc504898cda492e939', {
begin_message: 'Hey I am a virtual assistant calling from Retell Hospital.',
}) ;
console.log(llmResponse.llm_id) ;
You can include general_prompt in the request body to update the prompt content.
Note: If you want changes to take effect immediately without publishing from the dashboard, set your agent to use the Draft version at the phone number level. [(5) ]()AI Evy
01/13/2026, 4:56 PMAI Evy
01/13/2026, 4:56 PMnicottone
01/13/2026, 4:57 PMnicottone
01/13/2026, 4:58 PMAI Evy
01/13/2026, 4:58 PMAI Evy
01/13/2026, 4:58 PMbash
curl --request PATCH \
--url <https://api.retellai.com/update-retell-llm/%7Bllm_id%7D> \
--header 'Authorization: Bearer YOUR_API_KEY' \
--header 'Content-Type: application/json' \
--data '{
"general_prompt": "Your updated prompt here"
}'
, [(2) ]()
Replace:
- {llm_id} with your Retell LLM ID [(1) ]()
- YOUR_API_KEY with your Retell API key [(2) ]()
The general_prompt field is the prompt appended to the system prompt regardless of agent state. [(1) ]()AI Evy
01/13/2026, 4:58 PMAI Evy
01/13/2026, 4:58 PMnicottone
01/13/2026, 6:47 PMAI Evy
01/13/2026, 6:47 PMAI Evy
01/13/2026, 6:47 PMbash
curl --request PATCH \
--url <https://api.retellai.com/update-retell-llm/%7Bllm_id%7D> \
--header 'Authorization: Bearer YOUR_API_KEY' \
--header 'Content-Type: application/json' \
--data '{
"begin_message": "Hey I am a virtual assistant calling from Retell Hospital.",
"general_prompt": "You are ..."
}'
[(1) ]()
2. Update voice (Voice Agent) :
bash
curl --request PATCH \
--url <https://api.retellai.com/update-agent/%7Bagent_id%7D> \
--header 'Authorization: Bearer YOUR_API_KEY' \
--header 'Content-Type: application/json' \
--data '{
"voice_id": "11labs-Adrian"
}'
[(2) ]()
Key fields:
- `begin_message`: First utterance said by the agent in the call [(1) ]()
- `general_prompt`: Prompt appended to system prompt regardless of state
- `voice_id`: Unique voice id for the agent (find available voices in Dashboard) [(2) ]()
Replace {llm_id}, {agent_id}, and YOUR_API_KEY with your actual values.AI Evy
01/13/2026, 6:47 PMAI Evy
01/13/2026, 6:47 PM