# source-missing

An event leaves out its **[source](/docs/eventsourcingdb/sources)**.

- **Route:** `write-events`
- **Description:** `source is missing: expected a URI as defined by RFC 3986, such as 'https://library.eventsourcingdb.io'`
- **Details:** **`event`**, the place of the event in its list, counting from 0.

## Why It Happens

Every event names the system it comes from in its **`source`**, as **[CloudEvents](/docs/eventsourcingdb/cloud-events)** requires. The database reports this error when an event of a write **leaves out `source` or sends it as an empty string**. The source is the **first value of an event** that is checked, so an event that lacks more than its source reports this error first.

A typical cause is code that builds its events by hand and sets only the subject, the type, and the data.

## How to Fix It

Send a source with every event: a URI that names the system that writes it, such as `https://library.eventsourcingdb.io`. Sending the same request again fails the same way, since the error depends on the request alone.

## Example

For a write whose first event leaves out its source, EventSourcingDB answers with this error, as a line of the stream, and then ends the stream with its `end` item:

```json
{
  "type": "error",
  "data": {
    "code": "https://docs.eventsourcingdb.io/errors/source-missing",
    "description": "source is missing: expected a URI as defined by RFC 3986, such as 'https://library.eventsourcingdb.io'",
    "details": {
      "event": 0
    }
  }
}
```