### Answer Based on the available sources, there's a known issue where importing conversation flow agents can fail with a "failed to get voice id" error when using custom voices [(1) ]() . This suggests the import process has strict validation requirements. When importing a conversation flow JSON, the system expects specific required fields in the correct format. According to the API documentation, the core required fields for creating a conversation flow include [(2) ]() : -

model_choice

(object with

model

and

type

properties) -

nodes

(array of node objects, each with

id

,

type

, and

instruction

properties) -

start_speaker

(enum: "user" or "agent") The error "cannot read properties of undefined (reading 'type') " suggests the import parser is trying to access a

type

property on an undefined object. This commonly occurs when: 1. **Node structure issues**: Each node must have a

type

field (e.g., "conversation", "function", etc.) 2. **Model choice configuration**: The

model_choice

object must include a

type

field (e.g., "cascading") 3. **Tool definitions**: If you have tools, each must have a

type

field (e.g., "custom") To troubleshoot, verify that every node in your

nodes

array has a properly defined

type

field, and that your

model_choice

object includes both

model

and

type

properties . If the issue persists after validation, I recommend reaching out to support through the [Documentation]() or [hiring a certified Retell partner]() for assistance with the specific JSON structure causing the error.

​ To learn more, see the sources I considered: [[1] Conversation Flow: Import / Upload JSON](https://discord.com/channels/1186424376300679209/1394595851942367252) [[2] Create Conversation Flow](https://docs.retellai.com/api-references/create-conversation-flow) ​

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

@AI Evy "Hi, I'm getting this error when trying to import a conversation flow agent JSON: 'failed to import agent configuration — cannot read properties of undefined (reading type)' I've already tried: Removing all server-generated fields (agent_id, version, is_published, last_modification_timestamp) Fixing variable names to remove {{ }} brackets Removing tool_type: local from function nodes Removing instruction from end nodes Changing language from multi to en-US and back Removing the voice_id entirely Rebuilding the JSON completely from scratch with only bare minimum fields Nothing has worked. Can someone tell me exactly which field or structure is causing this error? I'm happy to share the JSON file directly. The agent is a conversation flow with 7 nodes: Welcome, Info/Booking Intake, Check Availability (function), Collect Customer Info (extract_dynamic_variables), Book Appointment (function), Goodbye, and End Call. It uses two Cal.com tools." https://cdn.discordapp.com/attachments/1480750530107150346/1480752221611364362/Mazz_Barbershop_MINIMAL.json?ex=69b0d178&is=69af7ff8&hm=794fd6aa8a75561820d0147e783ffd1f120def0085905078eadae892c16c6339&

### Answer The "cannot read properties of undefined (reading 'type') " error typically occurs when required fields are missing or improperly structured in your conversation flow JSON [(1) ]() . Based on the conversation flow structure requirements, verify these critical fields are present and correctly formatted : Required top-level fields: -

model_choice

- must include both

model

and

type

properties -

start_speaker

- must be either "user" or "agent" -

nodes

- array of node objects For each node in your nodes array, ensure: -

id

field is present -

type

field is present (e.g., "conversation", "function", "extract_dynamic_variables", "end_call") -

instruction

object with

type

and appropriate content For function nodes specifically: - Each edge must have a

transition_condition

with a

type

field - Tools referenced must have a

type

field (e.g., "custom") For your extract_dynamic_variables node: - Ensure the node structure includes the required

type

field Since you mentioned using Cal.com tools, verify each tool definition in your

tools

array has : -

type

field (typically "custom") -

name

field -

description

field The error suggests the parser is encountering an undefined object when trying to access its

type

property. Double-check that every object that should have a

type

field actually has one defined, particularly in your nodes array, model_choice object, and tools array . If you've verified all these fields and the issue persists, reach out through the [Documentation]() or [hire a certified Retell partner]() for direct assistance with your specific JSON structure.

​ To learn more, see the sources I considered: [[1] Create Conversation Flow](https://docs.retellai.com/api-references/create-conversation-flow) ​

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