I’m creating outbound calls via the Create Phone Call API and passing docto... Retell AI #❓・ai-evy-support

I’m creating outbound calls via the Create Phone C...

punk8357

01/23/2026, 8:44 PM

@AI Evy I’m creating outbound calls via the Create Phone Call API and passing doctor-specific instructions at call time, but the agent isn’t using them. Details: Agent type: Multi-Prompt Agent Call creation succeeds (call_status = registered) I pass data like this in the API request: { "agent_id": "...", "to_number": "...", "from_number": "...", "dynamic_variables": { "instructions": "Ask about chest pain, syncope, meds, allergies", "on_behalf_of": "Dr X" } } In the agent prompt, I reference them explicitly: You are calling on behalf of {{on_behalf_of}}. You must ask every question listed in {{instructions}}. However, when the call happens, the agent ignores the instructions and just follows its default flow. Questions: Is dynamic_variables the correct field for injecting call-time instructions? Do Multi-Prompt agents fully support dynamic variables, or is there a limitation? Do dynamic variables need to be enabled/configured anywhere in the dashboard beyond referencing them in the prompt?

AI Evy

01/23/2026, 8:44 PM

Thanks for tagging me @punk8357. I'll look through relevant sources and get back to you shortly.

AI Evy

01/23/2026, 8:44 PM

Feel free to tag @AI Evy with additional questions. I also appreciate feedback, it helps me improve.

AI Evy

01/23/2026, 8:44 PM

### Answer The issue is the field name you're using. The correct field is

retell_llm_dynamic_variables

, not

dynamic_variables

. [(1) ]() Your API request should look like this:

Copy code

json
{
  "agent_id": "...",
  "to_number": "...",
  "from_number": "...",
  "retell_llm_dynamic_variables": {
    "instructions": "Ask about chest pain, syncope, meds, allergies",
    "on_behalf_of": "Dr X"
  }
}

Note that all values must be strings. [(2) ]() To answer your specific questions: 1. Correct field name: Use

retell_llm_dynamic_variables

, not

dynamic_variables

. [(1) ]() 2. Multi-Prompt agent support: Dynamic variables work in prompts across agent types. The documentation confirms they can be used in prompts, begin message, tool configurations, and more. [(2) ]() 3. Dashboard configuration: You can optionally set default values for dynamic variables at the agent level in the dashboard, which serve as fallbacks when variables aren't included in the call request. Beyond that, you just need to reference them in your prompt using the

{{variable_name}}

syntax. Tip: You can verify your variables are being received by checking the call response—it should include

retell_llm_dynamic_variables

with your values if they were passed correctly. A community member experienced a similar issue and confirmed the variables weren't reaching Retell when using the wrong field name. [(3) ]()

AI Evy

01/23/2026, 8:44 PM

To learn more, see the sources I considered: [[1] Create Phone Call](https://docs.retellai.com/api-references/create-phone-call) [[2] Dynamic Variables](https://docs.retellai.com/build/dynamic-variables) [[3] dynamic variables ignored by agent.](https://discord.com/channels/1186424376300679209/1390663797517062204)

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