create_agent
Creates a new Retell agent
LABSCO SUMMARY
The agent's configuration and its call log are reachable in the same session that is debugging it.
The four-way split — agent, Retell LLM, phone number, call — runs right through the tool set, and it is the thing to internalise first: changing what the agent says means updating the Retell LLM, while changing how it sounds means updating the agent. Edits to an agent are versioned, which is why get_agent_versions exists and why a bad prompt change is traceable. Calls are created and read here, not steered: nothing interrupts, transfers or mutes a call in progress.
What it is
A server over the Retell API, following its object model — calls, agents, phone numbers, voices and Retell LLM configurations, each with its own tools.
What you get
- Calls placed two ways — outbound from one number to another, or in the browser against an agent — both accepting dynamic variables and metadata, with per-call opt-out of sensitive data storage
- Call records listed by agent and time window, fetched by ID, updated with new metadata or dynamic variables, and deleted
- Agents created from a voice, language and response engine, then tuned: backchannel behaviour and words, ambient sound and its volume, boosted keywords and the delay before the opening line
- Every edit to an agent kept as a version, listed with get_agent_versions
- Numbers provisioned by area code and wired to an inbound agent, an outbound agent and an inbound webhook URL
- Retell LLM configurations as separate objects: general prompt, general tools, knowledge base IDs, model and temperature, changed without touching the agent
Requirements
RETELL_API_KEY, and a Retell account whose agents, numbers and calls that key can reach.
Setup effort
One command plus a key — npx -y @abhaybabbar/retellai-mcp-server, then supply credentials
USE CASES
01
Launching an outbound call run
Pick the number to dial from, place the calls with per-call dynamic variables, and read the results back by agent and time window once they finish.
02
Standing up a new inbound line
Create the agent that will answer, provision a number in the area code you want, and point the number at that agent along with the webhook that should receive inbound events.
03
Changing what the agent says
The wording lives in the Retell LLM, not the agent: read the current configuration, edit the general prompt, tools or knowledge base IDs, and leave the voice untouched.
04
Tuning how the agent sounds
Audition the available voices, assign one, then adjust the conversational feel — backchannel words, ambient sound, boosted keywords, the pause before the first line. Each change becomes a new agent version.
24 tools
Counted once with only startup setup. Other versions, modes or optional credentials may expose a different list.
create_phone_call
Creates a new phone call
create_phone_number
Creates a new phone number
create_retell_llm
Creates a new Retell LLM
create_web_call
Creates a new web call
delete_agent
Deletes a Retell agent
delete_call
Deletes a call
delete_phone_number
Deletes a phone number
delete_retell_llm
Deletes a Retell LLM
get_agent
Gets a Retell agent by ID
get_agent_versions
Gets all versions of a Retell agent
get_call
Gets a call by ID
get_phone_number
Gets details of a specific phone number
get_retell_llm
Gets a Retell LLM by ID
get_voice
Gets details of a specific voice
list_agents
Lists all Retell agents
list_calls
Lists all calls
list_phone_numbers
Lists all Retell phone numbers
list_retell_llms
Lists all Retell LLMs
list_voices
Lists all available Retell voices
update_agent
Updates an existing Retell agent
update_call
Updates an existing call
update_phone_number
Updates a phone number
update_retell_llm
Updates an existing Retell LLM
BEFORE YOU INSTALL
What to know first
Tools you get
24 tools when we connected.
Requires
- npx on PATH
- RETELL_API_KEY in your environment
Where it runs
The documented client runs the server on your machine.
CONTEXT COST
Moderate Standing cost
Rated by the size of the 24 tool definitions that ride along on every turn, not by how many there are
INSTALLATION
Connect your client
Server setup
TERMINAL
npx -y @abhaybabbar/retellai-mcp-serverMCP Clients
Claude Desktop
CLAUDE DESKTOP · JSON
{
"mcpServers": {
"retellai-mcp-server": {
"command": "npx",
"args": [
"-y",
"@abhaybabbar/retellai-mcp-server"
],
"env": {
"RETELL_API_KEY": "<YOUR_RETELL_API_KEY>"
}
}
}
}
