SendKit
Cold-email infrastructure with a dedicated IP per account, campaigns, sequences, leads, DNC, and a deliverability surface (mailbox health, warmup, inbox-placement and blacklist tests). BYOK; free on hyreflow.
Use SendKit for outbound email campaign management: create and sequence campaigns, push leads, start and pause sending, and pull analytics. SendKit's differentiator is dedicated-IP deliverability, it's the sequencer whose mailbox health, warmup progress and inbox-placement/blacklist tests you can read through the API, so a play can confirm a mailbox is ready before it sends instead of finding out from the bounce rate.
Free on hyreflow (0 credits): runs on your own connected SendKit account.
Capabilities
| Tool | Does | Cost |
|---|---|---|
list_campaigns | List campaigns (resolve a stable campaign ID) | Free |
create_campaign | Create a campaign: draft, nothing sends yet | Free |
update_campaign | Update a campaign's sequence/schedule/settings | Free |
add_campaign_leads | Add leads to a campaign (up to 5,000 per call) | Free |
start_campaign | Start sending: requires a mailbox, a sequence step, a lead | Free |
pause_campaign / resume_campaign | Pause or resume sending | Free |
get_campaign_analytics | Sent / opened / clicked / replied / bounced | Free |
list_leads / create_lead / create_leads_bulk | Manage the workspace-wide lead pool | Free |
list_dnc / add_dnc_entries | Read and add do-not-contact entries | Free |
list_mailboxes / get_mailbox_health | Mailbox status, bounce rate, health score | Free |
list_warmup_stats / get_warmup_config | Warmup progress and configuration per mailbox | Free |
create_inbox_placement_test | Send a seed test to check inbox placement | Free |
create_blacklist_test | Check a mailbox against blacklists | Free |
Guidance
- Auth is a workspace key (
sk_...), created in the SendKit UI under its API settings. A platform key (sk_user_...) needs a workspace header this integration doesn't send, so connecting one is rejected up front rather than passing a check and failing on every real call later. - Check deliverability before you send. Read
get_mailbox_healthand the warmup endpoints for a mailbox before assigning it to a campaign, not only once at connection time. - Gate activation behind enrichment/verification: only push leads that have been validated.
start_campaignandresume_campaigntrigger real outbound; confirm the mailbox, sequence and lead list first. - Resolve campaign IDs from
list_campaignsbefore any write. - Add or bulk-create leads in batches of up to 5,000 per call.
- Writes are at-least-once. A rate-limited or 5xx response is retried automatically, so a write
whose reply was lost after it landed can apply twice. Enrolling leads is safe, SendKit skips
ones already in the campaign, and bulk lead creation skips duplicates by email.
create_campaignand the two deliverability tests are not: read back before re-issuing one yourself.
hyreflow tools execute sendkit add_campaign_leads \
--payload '{"campaign_id":"campaign_123","leads":[{"email":"[email protected]","firstName":"Ada","companyName":"Acme"}]}'Building a campaign is free; sending is the irreversible step. Keep start_campaign behind an
explicit approval gate: see Campaign Plays.
Reply.io
Multichannel outreach: email plus LinkedIn steps and calls in one sequence, with an AI-SDR layer. Key gotcha: scope model gates writes, and start_sequence is approval-gated.
Serper
Fast, broad Google search + Maps results. A discovery/recall layer, validate important hits, don't treat as ground truth.