Skip to main content

The official Python library for the retell API

Project description

Retell Python API library

PyPI version

The Retell Python library provides convenient access to the Retell REST API from any Python 3.7+ application. The library includes type definitions for all request params and response fields, and offers both synchronous and asynchronous clients powered by httpx.


The REST API documentation can be found on The full API of this library can be found in


# install from PyPI
pip install retell-sdk


The full API of this library can be found in

from retell import Retell

client = Retell(

agent_response = client.agent.create(

Async usage

Simply import AsyncRetell instead of Retell and use await with each API call:

import asyncio
from retell import AsyncRetell

client = AsyncRetell(

async def main() -> None:
    agent_response = await client.agent.create(

Functionality between the synchronous and asynchronous clients is otherwise identical.

Using types

Nested request parameters are TypedDicts. Responses are Pydantic models which also provide helper methods for things like:

  • Serializing back into JSON, model.to_json()
  • Converting to a dictionary, model.to_dict()

Typed requests and responses provide autocomplete and documentation within your editor. If you would like to see type errors in VS Code to help catch bugs earlier, set python.analysis.typeCheckingMode to basic.

Handling errors

When the library is unable to connect to the API (for example, due to network connection problems or a timeout), a subclass of retell.APIConnectionError is raised.

When the API returns a non-success status code (that is, 4xx or 5xx response), a subclass of retell.APIStatusError is raised, containing status_code and response properties.

All errors inherit from retell.APIError.

import retell
from retell import Retell

client = Retell()

except retell.APIConnectionError as e:
    print("The server could not be reached")
    print(e.__cause__)  # an underlying Exception, likely raised within httpx.
except retell.RateLimitError as e:
    print("A 429 status code was received; we should back off a bit.")
except retell.APIStatusError as e:
    print("Another non-200-range status code was received")

Error codes are as followed:

Status Code Error Type
400 BadRequestError
401 AuthenticationError
403 PermissionDeniedError
404 NotFoundError
422 UnprocessableEntityError
429 RateLimitError
>=500 InternalServerError
N/A APIConnectionError


Certain errors are automatically retried 2 times by default, with a short exponential backoff. Connection errors (for example, due to a network connectivity problem), 408 Request Timeout, 409 Conflict, 429 Rate Limit, and >=500 Internal errors are all retried by default.

You can use the max_retries option to configure or disable retry settings:

from retell import Retell

# Configure the default for all requests:
client = Retell(
    # default is 2

# Or, configure per-request:


By default requests time out after 1 minute. You can configure this with a timeout option, which accepts a float or an httpx.Timeout object:

from retell import Retell

# Configure the default for all requests:
client = Retell(
    # 20 seconds (default is 1 minute)

# More granular control:
client = Retell(
    timeout=httpx.Timeout(60.0, read=5.0, write=10.0, connect=2.0),

# Override per-request:

On timeout, an APITimeoutError is thrown.

Note that requests that time out are retried twice by default.



We use the standard library logging module.

You can enable logging by setting the environment variable RETELL_LOG to debug.

$ export RETELL_LOG=debug

How to tell whether None means null or missing

In an API response, a field may be explicitly null, or missing entirely; in either case, its value is None in this library. You can differentiate the two cases with .model_fields_set:

if response.my_field is None:
  if 'my_field' not in response.model_fields_set:
    print('Got json like {}, without a "my_field" key present at all.')
    print('Got json like {"my_field": null}.')

Accessing raw response data (e.g. headers)

The "raw" Response object can be accessed by prefixing .with_raw_response. to any HTTP method call, e.g.,

from retell import Retell

client = Retell()
response = client.agent.with_raw_response.create(

agent = response.parse()  # get the object that `agent.create()` would have returned

These methods return an APIResponse object.

The async client returns an AsyncAPIResponse with the same structure, the only difference being awaitable methods for reading the response content.


The above interface eagerly reads the full response body when you make the request, which may not always be what you want.

To stream the response body, use .with_streaming_response instead, which requires a context manager and only reads the response body once you call .read(), .text(), .json(), .iter_bytes(), .iter_text(), .iter_lines() or .parse(). In the async client, these are async methods.

with client.agent.with_streaming_response.create(
) as response:

    for line in response.iter_lines():

The context manager is required so that the response will reliably be closed.

Making custom/undocumented requests

This library is typed for convenient access to the documented API.

If you need to access undocumented endpoints, params, or response properties, the library can still be used.

Undocumented endpoints

To make requests to undocumented endpoints, you can make requests using client.get,, and other http verbs. Options on the client will be respected (such as retries) will be respected when making this request.

import httpx

response =
    body={"my_param": True},


Undocumented request params

If you want to explicitly send an extra param, you can do so with the extra_query, extra_body, and extra_headers request options.

Undocumented response properties

To access undocumented response properties, you can access the extra fields like response.unknown_prop. You can also get all the extra fields on the Pydantic model as a dict with response.model_extra.

Configuring the HTTP client

You can directly override the httpx client to customize it for your use case, including:

  • Support for proxies
  • Custom transports
  • Additional advanced functionality
from retell import Retell, DefaultHttpxClient

client = Retell(
    # Or use the `RETELL_BASE_URL` env var

Managing HTTP resources

By default the library closes underlying HTTP connections whenever the client is garbage collected. You can manually close the client using the .close() method if desired, or with a context manager that closes when exiting.


This package generally follows SemVer conventions, though certain backwards-incompatible changes may be released as minor versions:

  1. Changes that only affect static types, without breaking runtime behavior.
  2. Changes to library internals which are technically public but not intended or documented for external use. (Please open a GitHub issue to let us know if you are relying on such internals).
  3. Changes that we do not expect to impact the vast majority of users in practice.

We take backwards-compatibility seriously and work hard to ensure you can rely on a smooth upgrade experience.

We are keen for your feedback; please open an issue with questions, bugs, or suggestions.


Python 3.7 or higher.

Project details

Download files

Download the file for your platform. If you're not sure which to choose, learn more about installing packages.

Source Distribution

retell_sdk-3.18.0.tar.gz (77.8 kB view hashes)

Uploaded Source

Built Distribution

retell_sdk-3.18.0-py3-none-any.whl (110.4 kB view hashes)

Uploaded Python 3

Supported by

AWS AWS Cloud computing and Security Sponsor Datadog Datadog Monitoring Fastly Fastly CDN Google Google Download Analytics Microsoft Microsoft PSF Sponsor Pingdom Pingdom Monitoring Sentry Sentry Error logging StatusPage StatusPage Status page