diff --git a/action.yml b/action.yml
index 91d3982..99b9194 100644
--- a/action.yml
+++ b/action.yml
@@ -4,11 +4,13 @@ inputs:
   repository:
     description: 'Repository name with owner. For example, actions/checkout'
     default: ${{ github.repository }}
+    required: false
   ref:
     description: >
       The branch, tag or SHA to checkout. When checking out the repository that
       triggered a workflow, this defaults to the reference or SHA for that
       event.  Otherwise, uses the default branch.
+    required: false
   token:
     description: >
       Personal access token (PAT) used to fetch the repository. The PAT is configured
@@ -22,6 +24,7 @@ inputs:
 
       [Learn more about creating and using encrypted secrets](https://help.github.com/en/actions/automating-your-workflow-with-github-actions/creating-and-using-encrypted-secrets)
     default: ${{ github.token }}
+    required: false
   ssh-key:
     description: >
       SSH key used to fetch the repository. The SSH key is configured with the local
@@ -34,31 +37,39 @@ inputs:
 
       [Learn more about creating and using
       encrypted secrets](https://help.github.com/en/actions/automating-your-workflow-with-github-actions/creating-and-using-encrypted-secrets)
+    required: false
   ssh-known-hosts:
     description: >
       Known hosts in addition to the user and global host key database. The public
       SSH keys for a host may be obtained using the utility `ssh-keyscan`. For example,
       `ssh-keyscan github.com`. The public key for github.com is always implicitly added.
+    required: false
   ssh-strict:
     description: >
       Whether to perform strict host key checking. When true, adds the options `StrictHostKeyChecking=yes`
       and `CheckHostIP=no` to the SSH command line. Use the input `ssh-known-hosts` to
       configure additional hosts.
     default: true
+    required: false
   persist-credentials:
     description: 'Whether to configure the token or SSH key with the local git config'
     default: true
+    required: false
   path:
     description: 'Relative path under $GITHUB_WORKSPACE to place the repository'
+    required: false
   clean:
     description: 'Whether to execute `git clean -ffdx && git reset --hard HEAD` before fetching'
     default: true
+    required: false
   fetch-depth:
     description: 'Number of commits to fetch. 0 indicates all history for all branches and tags.'
     default: 1
+    required: false
   lfs:
     description: 'Whether to download Git-LFS files'
     default: false
+    required: false
   submodules:
     description: >
       Whether to checkout submodules: `true` to checkout submodules or `recursive` to
@@ -68,6 +79,7 @@ inputs:
       When the `ssh-key` input is not provided, SSH URLs beginning with `git@github.com:` are
       converted to HTTPS.
     default: false
+    required: false
 runs:
   using: node12
   main: dist/index.js