> ## Documentation Index
> Fetch the complete documentation index at: https://docs.encord.com/llms.txt
> Use this file to discover all available pages before exploring further.

# FastAPI

<Info>
  The following example shows the general structure of how to build a FastAPI application. For concrete implementations of agents with specific abilities, see the [examples section](/agents-documentation/Custom-Agents/Examples).
</Info>

## STEP 1: Create a Project

1. Create a new Encord Project:

```shell theme={"dark"}
mkdir my_project
cd my_project
```

2. Create and source a new virtual environment.

```
python -m venv venv
source venv/bin/activate
```

3. Install dependencies.

```shell theme={"dark"}
python -m pip install "fastapi[standard]" encord-agents
```

## STEP 2: Define the Agent

Create a `main.py` file using the following template:

```python title="main.py" theme={"dark"}
from typing_extensions import Annotated

from encord.objects.ontology_labels_impl import LabelRowV2
from encord_agents import FrameData
from encord_agents.fastapi import dep_label_row
from encord_agents.fastapi.cors import EncordCORSMiddleware

from fastapi import FastAPI, Depends, Form

app = FastAPI()
app.add_middleware(EncordCORSMiddleware)

@app.post("/my_agent")
def my_agent(
    frame_data: FrameData,
    label_row: Annotated[LabelRowV2, Depends(dep_label_row)],
):
    # ... Do your edits to the labels
    label_row.save()
```

Complete the `my_agent` function with the logic you want to execute when the agent is triggered.

<Tip>
  You can inject multiple different [dependencies](/agents-documentation/Reference/Custom-Agents/Agents-Reference-Custom-Agents#Dependencies-2) into the function if necessary.
</Tip>

You can find multiple examples of what can be done with Custom Agents [here](/agents-documentation/Custom-Agents/Examples/GCP-Examples).

## STEP 3: Test the Agent

Trigger the agent by running it locally.

```shell theme={"dark"}
ENCORD_SSH_KEY_FILE=/path/to/your_private_key \
    fastapi dev main.py --port 8080
```

<Info>
  This means starting an API at `localhost:8080/my_agent` that expects a POST request with `JSON` data with the following format:

  ```json theme={"dark"}
  {
      "projectHash": "<project_hash>",
      "dataHash": "<data_hash>",
      "frame": <frame_number>
  }
  ```
</Info>

To test the agent endpoint, open the [Label Editor](/platform-documentation/Annotate/annotate-label-editor) in your browser on a frame where you want to run the agent. Then, copy the URL.

Open a new terminal in the `my_project` directory and run:

```shell theme={"dark"}
source venv/bin/activate
encord-agents test local my_agent '<the_pasted_url>'
```

<Warning>
  The single quotes around `<the_pasted_url>` are important and should be there because you might copy a url with, e.g., an `&` character that have a [special meaning](https://www.howtogeek.com/439199/15-special-characters-you-need-to-know-for-bash/#amp-background-process) if it is not within a string (or escaped).
</Warning>

Refresh the Label Editor in your browser to see the effect.

## STEP 4: Deployment

<Warning>
  This section is under construction.
</Warning>

Meanwhile, refer to the [official FastAPI documentation](https://fastapi.tiangolo.com/deployment/).