Add up to 10,000 addresses.

All or nothing: one invalid address makes the whole batch 400 (data.invalid, the first 100; reasons format, checksum); a batch that would take the subscription past 1,000,000 distinct addresses is 409 limit_reached with data.limit: addresses_per_subscription and data.max: 1000000; a batch that would take the account past its address-pair limit is also 409 limit_reached; neither rejection writes addresses, counters or a change version, including under concurrent additions; when the platform capacity is full the call is a synchronous 503 service_unavailable and nothing is written. Set semantics: an address already watched, or repeated inside the request, counts as unchanged (the same address in different spellings is one address), so a resend is safe. After validation no item can fail, so the outcome of each item is reported as counts. The address applies to every chain listed in chains of the subscription and to no other chain. Changes apply within about a second; a chain matches the new addresses from its applied_from_block, not retroactively (replay cannot bring earlier events: it re-delivers stored matches and these addresses had none; use the Data API by address). change_version is applied on every chain once applied_version of the subscription reaches it.