Fix issues and improve CI tunnel doc

doc/user/clusters/agent/ci_cd_tunnel.md

@@ -9,17 +9,19 @@ info: To determine the technical writer assigned to the Stage/Group associated w
 > [Introduced](https://gitlab.com/gitlab-org/gitlab/-/issues/327409) in GitLab 14.1.
 
 The CI/CD Tunnel enables users to access Kubernetes clusters from GitLab CI/CD jobs even if there is no network
-connectivity between GitLab Runner and a cluster. In the current iteration, only CI/CD jobs in the Configuration project
-are able to access one of the configured agents. GitLab Runner does not have to be running in the same cluster.
+connectivity between GitLab Runner and a cluster. GitLab Runner does not have to be running in the same cluster.
 
-Prerequisistes:
+Only CI/CD jobs set in the configuration project can access one of the configured agents.
+
+Prerequisites:
 
 - A running [`kas` instance](index.md#set-up-the-kubernetes-agent-server).
-- A [Configuration repository](index.md#define-a-configuration-repository) with an Agent config file installed (`.gitlab/agents/<agent-name>/config.yaml`).
+- A [configuration repository](index.md#define-a-configuration-repository) with an Agent config file
+  installed (`.gitlab/agents/<agent-name>/config.yaml`).
 - An [Agent record](index.md#create-an-agent-record-in-gitlab).
 - The agent is [installed in the cluster](index.md#install-the-agent-into-the-cluster).
 
-To create the Tunnel:
+To access your cluster from a CI/CD job through the tunnel:
 
 1. In your `.gitlab-ci.yml` add a section that creates a `kubectl` compatible configuration file (`kubecontext`) and use it in one
    or more jobs:
@@ -27,34 +29,39 @@ To create the Tunnel:
    ```yaml
    variables:
      AGENT_ID: 4 # agent id that you got when you created the agent record
+     KUBE_CFG_FILE: "$CI_PROJECT_DIR/.kubeconfig.agent.yaml"
 
    .kubectl_config: &kubectl_config
      - |
-       cat << EOF > "$CI_PROJECT_DIR/.kubeconfig.agent.yaml"
+       cat << EOF > "$KUBE_CFG_FILE"
        apiVersion: v1
        kind: Config
        clusters:
-       - cluster:
-           server: https://kas.gitlab.com/k8s-proxy
-         name: agent
+       - name: agent
+         cluster:
+           server: https://kas.gitlab.com/k8s-proxy/
        users:
        - name: agent
          user:
            token: "ci:$AGENT_ID:$CI_JOB_TOKEN"
        contexts:
-       - context:
-         cluster: agent
+       - name: agent
+         context:
+           cluster: agent
            user: agent
-           name: agent
        current-context: agent
        EOF
 
    deploy:
+     image:
+       name: bitnami/kubectl:latest
+       entrypoint: [""]
      script:
      - *kubectl_config
-     - kubectl --kubeconfig="$CI_PROJECT_DIR/.kubeconfig.agent.yaml" get pods
+     - kubectl --kubeconfig="$KUBE_CFG_FILE" get pods
    ```
 
 1. Execute `kubectl` commands directly against your cluster with this CI/CD job you just created.
 
-We are [working to automate the first step](https://gitlab.com/gitlab-org/gitlab/-/issues/324275) to simplify the process.
+We are working on [creating the configuration file automatically](https://gitlab.com/gitlab-org/gitlab/-/issues/324275)
+to simplify the process.