Daml JSON API Python API Docs | dltHub

The Daml JSON API provides a RESTful interface for interacting with the Daml ledger, requiring a JSON Web Token for authentication. It supplements the lower-level Ledger API with an easy-to-use server component. The API supports both HTTP and gRPC-web protocols. The REST API base URL is `` and All requests require a Bearer JWT token for authentication..

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 Daml JSON API data in under 10 minutes.

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What data can I load from Daml JSON API?

Here are some of the endpoints you can load from Daml JSON API:

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How do I authenticate with the Daml JSON API API?

Authentication is performed via a Bearer JWT token passed in the HTTP Authorization header (e.g., Authorization: Bearer <your_jwt>).

1. Get your credentials

1. Install the Daml SDK if not already installed.
2. Start the Daml sandbox or connect to your ledger.
3. Use the daml json-api command with the --jwt flag to generate a development token, e.g., daml json-api --jwt <path-to-jwt>.
4. For production, request a JWT from your identity provider or the ledger administrator according to your organization’s security policy.
5. Copy the generated JWT and store it securely for use in API calls.

2. Add them to .dlt/secrets.toml

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[sources.daml_json_api_source]
token = "your_jwt_here"

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 Daml JSON API 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 daml_json_api_pipeline.py

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

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Pipeline daml_json_api_pipeline load step completed in 0.26 seconds
1 load package(s) were loaded to destination duckdb and into dataset daml_json_api_data
The duckdb destination used duckdb:/daml_json_api.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 daml_json_api_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 query and packages from the Daml JSON API 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 daml_json_api_source(token=dlt.secrets.value):
    config: RESTAPIConfig = {
        "client": {
            "base_url": "",
            "auth": {
                "type": "bearer",
                "token": token,
            },
        },
        "resources": [
            {"name": "query", "endpoint": {"path": "v1/query", "data_selector": "result"}},
            {"name": "packages", "endpoint": {"path": "v1/packages", "data_selector": "result"}}
        ],
    }
    yield from rest_api_resources(config)


def get_data() -> None:
    pipeline = dlt.pipeline(
        pipeline_name="daml_json_api_pipeline",
        destination="duckdb",
        dataset_name="daml_json_api_data",
    )
    load_info = pipeline.run(daml_json_api_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("daml_json_api_pipeline").dataset()
sessions_df = data.query.df()
print(sessions_df.head())

SQL (DuckDB example):

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SELECT * FROM daml_json_api_data.query LIMIT 10;

In a marimo or Jupyter notebook:

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import dlt

data = dlt.pipeline("daml_json_api_pipeline").dataset()
data.query.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 Daml JSON API 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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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