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Check which messaging service is currently available for an E.164 phone number. This is a read-only lookup and does not require an agent identity or an existing conversation.

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Check messaging capability

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Query parameters

URL-encode the leading + as %2B when you place the number in the query string:
bash
Use an admin API key or claimed agent key. Unclaimed (mid-signup) agent keys are rejected.

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Response (200)

The response body is a JSON string—not an object—and is always one of iMessage, SMS, or RCS:
JSON
Check capability close to the time you intend to message the recipient because service availability can change.

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Error responses