Castor EDC Python API Docs | dltHub

Castor EDC is a cloud‑based electronic data capture platform for clinical research that offers a REST API for programmatic access to study data. The REST API base URL is https://data.castoredc.com/api and All requests require a Bearer token obtained via OAuth2 client‑credentials..

dlt is an open-source Python library that handles authentication, pagination, and schema evolution automatically. dlthub provides AI context files that enable code assistants to generate production-ready pipelines. Install with uv pip install "dlt[workspace]" and start loading Castor EDC data in under 10 minutes.

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What data can I load from Castor EDC?

Here are some of the endpoints you can load from Castor EDC:

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How do I authenticate with the Castor EDC API?

The API uses OAuth2 Client Credentials flow; obtain an access token with client_id and client_secret and include it as a Bearer token in the Authorization header of each request.

1. Get your credentials

1. Log in to Castor EDC and open your User Settings page.
2. Generate a new API Client ID and Client Secret.
3. Make a POST request to https://data.castoredc.com/api/oauth/token with parameters: client_id, client_secret, grant_type=client_credentials. The response contains the access token to be used in subsequent calls.

2. Add them to .dlt/secrets.toml

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[sources.castor_edc_source]
client_id = "your_client_id"
client_secret = "your_client_secret"

dlt reads this automatically at runtime — never hardcode tokens in your pipeline script. For production environments, see setting up credentials with dlt for environment variable and vault-based options.

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How do I set up and run the pipeline?

Set up a virtual environment and install dlt:

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uv venv && source .venv/bin/activate
uv pip install "dlt[workspace]"

1. Install the dlt AI Workbench:

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dlt ai init --agent <your-agent> # <agent>: claude | cursor | codex

This installs project rules, a secrets management skill, appropriate ignore files, and configures the dlt MCP server for your agent. Learn more →

2. Install the rest-api-pipeline toolkit:

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dlt ai toolkit rest-api-pipeline install

This loads the skills and context about dlt the agent uses to build the pipeline iteratively, efficiently, and safely. The agent uses MCP tools to inspect credentials — it never needs to read your secrets.toml directly. Learn more →

3. Start LLM-assisted coding:

Use /find-source to load data from the Castor EDC API into DuckDB.

The rest-api-pipeline toolkit takes over from here — it reads relevant API documentation, presents you with options for which endpoints to load, and follows a structured workflow to scaffold, debug, and validate the pipeline step by step.

4. Run the pipeline:

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python castor_edc_pipeline.py

If everything is configured correctly, you'll see output like this:

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Pipeline castor_edc_pipeline load step completed in 0.26 seconds
1 load package(s) were loaded to destination duckdb and into dataset castor_edc_data
The duckdb destination used duckdb:/castor_edc.duckdb location to store data
Load package 1749667187.541553 is LOADED and contains no failed jobs

Inspect your pipeline and data:

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dlt pipeline castor_edc_pipeline show

This opens the Pipeline Dashboard where you can verify pipeline state, load metrics, schema (tables, columns, types), and query the loaded data directly.

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Python pipeline example

This example loads studies and study_data_points from the Castor EDC API into DuckDB. It mirrors the endpoint and data selector configuration from the table above:

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import dlt
from dlt.sources.rest_api import RESTAPIConfig, rest_api_resources

@dlt.source
def castor_edc_source(client_id=dlt.secrets.value):
    config: RESTAPIConfig = {
        "client": {
            "base_url": "https://data.castoredc.com/api",
            "auth": {
                "type": "bearer",
                "token": client_id,
            },
        },
        "resources": [
            {"name": "studies", "endpoint": {"path": "studies", "data_selector": "_embedded.studies"}},
            {"name": "subjects", "endpoint": {"path": "studies/{study_id}/subjects", "data_selector": "_embedded.subjects"}}
        ],
    }
    yield from rest_api_resources(config)


def get_data() -> None:
    pipeline = dlt.pipeline(
        pipeline_name="castor_edc_pipeline",
        destination="duckdb",
        dataset_name="castor_edc_data",
    )
    load_info = pipeline.run(castor_edc_source())
    print(load_info)

To add more endpoints, append entries from the resource table to the "resources" list using the same name, path, and data_selector pattern.

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How do I query the loaded data?

Once the pipeline runs, dlt creates one table per resource. You can query with Python or SQL.

Python (pandas DataFrame):

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import dlt

data = dlt.pipeline("castor_edc_pipeline").dataset()
sessions_df = data.studies.df()
print(sessions_df.head())

SQL (DuckDB example):

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SELECT * FROM castor_edc_data.studies LIMIT 10;

In a marimo or Jupyter notebook:

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import dlt

data = dlt.pipeline("castor_edc_pipeline").dataset()
data.studies.df().head()

See how to explore your data in marimo Notebooks and how to query your data in Python with dataset.

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What destinations can I load Castor EDC data to?

dlt supports loading into any of these destinations — only the destination parameter changes:

Change the destination in dlt.pipeline(destination="snowflake") and add credentials in .dlt/secrets.toml. See the full destinations list.

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Troubleshooting

Authentication Errors

• 401 Unauthorized – Occurs when the access token is missing, expired, or invalid. Obtain a fresh token via the /oauth/token endpoint using valid client credentials.

Rate Limiting

• 429 Too Many Requests – The API enforces a limit of 600 requests per 10 minutes. Implement retry‑after logic or reduce request frequency.

Pagination

• Most GET endpoints paginate results. Use query parameters page and page_size (default 10) to navigate through large result sets.

Ensure that the API key is valid to avoid 401 Unauthorized errors. Also, verify endpoint paths and parameters to avoid 404 Not Found errors.

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Next steps

Continue your data engineering journey with the other toolkits of the dltHub AI Workbench:

• data-exploration — Build custom notebooks, charts, and dashboards for deeper analysis with marimo notebooks.
• dlthub-runtime — Deploy, schedule, and monitor your pipeline in production.

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dlt ai toolkit data-exploration install
dlt ai toolkit dlthub-runtime install

• How to deploy a pipeline
• How to explore your data in marimo Notebooks
• How to query your data in Python with dataset
• Join the dlt community on Slack