E13001 — InvalidRecipient

Provide at least one recipient: a valid email address, a phone number in E.164 format, or both.

• HTTP status: 422
• Type: validation_error
• Name: InvalidRecipient

What to do

The request body parsed, but one or more values are invalid. Read the details array: each entry names the failing field (param, a dotted path like to[0].email) with a human-readable reason. Fix the named fields and retry.

Related

• E13xxx — Verify: every code in this range
• Errors: the full wire contract, status mapping, and error catalog
• Error handling: branching on type and code, validation details, and vendor_code