# `connection.value_invalid`

Connection's key holds a value it can't.

Area 11, [External services](../topics/external-services.md); not declinable; the next step is usually the agent's.

A credential is read from a secret setting, which code never sees:






```jadpo
application {
    connections: {
        couriers: {
            package: AcmeCouriers.v1
            domains: [shipping]
            credential: config.couriers_api_key
            environment: config.couriers_environment
        }
    }
}
```

```text
error: `couriers`'s credential must be a secret setting
 --> app.jadpo:6:25
  |
6 |             credential: config.couriers_api_key
  |                         ^^^^^^^^^^^^^^^^^^^^^^^ `couriers_api_key` isn't secret
  reason: A credential is read from the deployment's environment and never seen by code, so it is a `secret: true` setting, `config.<name>` (area 10, "Secrets").
  next: Add `secret: true` to `couriers_api_key` in `config.jadpo` (agent)
  rule: connection.value_invalid
  help: https://jadpo.dev/docs/errors/connection.value_invalid

check failed: 1 error, 6 files
```

`development: { sandbox: }` names the package's own operations and
resources:












```jadpo
application {
    connections: {
        couriers: {
            package: AcmeCouriers.v1
            domains: [shipping]
            environment: config.couriers_environment
            development: {
                sandbox: [bookings.creat]
            }
        }
    }
}
```

```text
error: `couriers`'s `sandbox:` lists `bookings.creat`, which `AcmeCouriers.v1` doesn't have
 --> app.jadpo:8:27
  |
8 |                 sandbox: [bookings.creat]
  |                           ^^^^^^^^^^^^^^ no such operation or resource
  reason: `sandbox:` lets the package's public operations and resources through to its sandbox in `jadpo dev`; `AcmeCouriers.v1` has `bookings.create` and `bookings`.
  next: Use `bookings.create` instead of `bookings.creat` (agent)
  rule: connection.value_invalid
  help: https://jadpo.dev/docs/errors/connection.value_invalid

check failed: 1 error, 12 files
```