Updates an existing transaction's metadata.

You can update both the label and metadata fields:

1. label: A string identifier used for future lookup or reporting.
2. metadata: A set of key-value string pairs for attaching structured, custom information to the transaction.

Note: Updating the metadata field will overwrite any existing metadata—not merge with it.

The endpoint returns a transaction with an updated label and metadata.

Authorization Scope

Only the merchant secret key is authorized to call this endpoint.