Check out example codes for "basecamp 3 api tag mention". It will help you in understanding the concepts better.

Code Example 1

<!-- tag/mention a person in Basecamp 3 programmatically -->
<bc-attachment sgid="attachable_sgid"></bc-attachment>

<!-- just replace "attachable_sgid" with the person's "attachable_sgid" like so  -->
<bc-attachment sgid="BAh4CEkiCGdpZAY5BkVUSSIpZ2lkOi7vYmMzL1BlcnNvbi8yOTMyMjg0Nz6leHBpcmVzX3luBjsAVEkiDHB2cnBvc2UGOwBUSSIPYXR0YWNoYWJsZQY7AFRJIg6leHBpcmVzX9F0BjsAVDA=--ef5255d2c4c5851416cf99664f59353825356876"></bc-attachment>

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