Istos, Apollo, Clay and Instantly: finding buyers without losing your voice
A fair, dated comparison of four sales tools, from big contact databases and data workflows to cold email at scale, and where an approval-first agent fits. Including how Istos works with Instantly.
I build Istos, so read this knowing that. Every claim about Apollo (opens in a new tab), Clay (opens in a new tab) and Instantly (opens in a new tab) below comes from their own websites, linked in the sources at the end and checked on 5 October 2026. Where a page didn't say something, I say so rather than guess. Prices change often in this market, so check the sources before you decide.
These four aren't really the same kind of product. Apollo is a full sales platform built around a very large contact database. Clay is data infrastructure for teams that build their own prospecting workflows. Instantly is cold email at scale, with sending accounts, warmup and a lead database. Istos is an agent that scores the leads you already have, writes one careful first email to each in your voice, and waits for you to approve it.
One relationship to be clear about up front: the Studio plan includes an Instantly integration, so approved lead emails can go out through your own Instantly workspace, with your own Instantly API key. On every other plan, and for anything you don't send through Instantly, an account sends from its own Gmail or its own mailbox. More on how it works below.
At a glance
Istos, Apollo, Clay and Instantly compared for finding buyers and sending a first email. Checked against each company's own website on 5 Oct 2026. Prices are in US dollars as their pages showed them; they change, so check the sources below before you decide.
What each one is for
Apollo says it gives you access to 240 million contacts and 30 million companies, and that over 600,000 companies use it. Around that data it offers sequences, a deliverability suite with email warmup, CRM integrations, waterfall enrichment, a Chrome extension, an AI assistant and a dialer. The free plan comes with 900 credits per seat a year. Paid plans are priced per seat: Basic at $49, Professional at $79 and Organization at $119 a month, each billed yearly, with Organization needing at least three seats.
Clay describes itself as infrastructure "to get any data, run agentic workflows, and launch GTM plays", and says it's trusted by more than 500,000 teams. It pulls data from more than 150 providers, can run several providers in a row until one finds an answer, and has an AI agent with web research, Claygent. Pricing is built from actions and data credits: a free plan with 6,000 actions and 1,200 data credits a year, Launch from $167 a month and Growth from $446 a month. Launch adds sending through Clay's own sequencer or an integration.
Instantly is built for sending. Every outreach plan includes unlimited email accounts and unlimited warmup. Growth is $47 a month for 5,000 emails and 1,000 uploaded contacts; Hypergrowth and Light Speed go up from there, and yearly billing is cheaper. Separately, its lead database of 450 million plus B2B leads runs on credits, from $47 a month for 1,500 credits, with enrichment, an AI email writer and a web research agent. Its own FAQ says that once your campaigns are set up, they run on autopilot.
Istos starts from leads you already have or can name: people you add, your LinkedIn connections on Pro, and companies Istos finds in the morning's tech news, from funding rounds to new offices and hiring. It scores each lead against checks you set, writes down why, and drafts one first email that sells one thing with one proof point from your own work. Every draft waits in your queue. Approved email goes from your own Gmail or mailbox, or on Studio through your own Instantly workspace.
How Istos and Instantly fit together
This is the one place where the products meet, so here it is exactly. It's part of the Studio plan, and you connect it yourself on Connections.
If you're on Studio, you paste your Instantly API key on Connections and Istos checks it with a read, nothing created. The key is stored encrypted for your account alone. Choose Instantly under Send lead emails through in Settings, and Istos uses your key to keep one campaign in your workspace, with a single step whose subject and body are filled per lead. You can point it at an existing campaign on Connections, but only one built that way. When you approve a lead email in Istos, that lead is added to the campaign with the exact subject and body you approved. Instantly then sends it from your warmed-up sending mailboxes inside the campaign's sending window. Your own personal address is left out of the sending list.
The campaign stops when the person replies, stops for their whole company once anyone there replies, and has open and link tracking turned off. Istos doesn't add steps or follow-ups inside Instantly, so nothing goes out there that you didn't approve in Istos.
You need your own paid Instantly plan for this. Istos isn't a reseller and there's no bundle. The split is simple: Istos decides who to write to and what to say, and you approve it. Instantly handles the sending infrastructure.
Where Istos fits
- You're writing to dozens, not thousands. A founder looking for the first ten customers, a freelancer pitching projects, a small studio. The bottleneck is a good note, not more contacts.
- You want it to sound like you. Every draft comes from your knowledge base and your voice rules, and it's under about 130 words with no hype.
- You want to see everything before it goes. One queue, every draft with its reason, nothing sent until you approve.
- You also hire or raise. The same account runs a job search and an investor pipeline, in the same voice.
Leads you already have, ranked and checked, on demo data.
Where they're stronger
- Finding contacts you don't have. Apollo, Clay and Instantly's lead database all give you people and emails. Istos doesn't. It works from your list, your network and the news.
- Volume and deliverability. Instantly and Apollo are built to send a lot of email safely, with warmup and deliverability tools. Istos sends one approved email at a time from your own Gmail or mailbox, or on Studio hands approved lead emails to your own Instantly workspace.
- Automated sequences. All three can run multi-step sequences on their own. Istos doesn't run sequences: anything it sends, a first email or a follow-up, waits for your approval.
- Data depth and workflows. Clay's enrichment across 150+ providers and its workflow builder go far beyond anything Istos does with data.
- CRM sync. Apollo and Clay sync with your CRM, and Instantly exports to the major ones. Istos has its own simple pipeline board.
- Track record. These are established products with hundreds of thousands of teams. Istos is new and in private beta.
When to choose them instead
- Choose Apollo (opens in a new tab) if you need a large pool of contacts and want data, sequences and calling in one tool, priced per seat.
- Choose Clay (opens in a new tab) if someone on your team builds prospecting workflows and you want the most complete data you can buy, with AI research on top.
- Choose Instantly (opens in a new tab) if you already know who to email and your challenge is sending a lot of it without landing in spam.
- Choose Istos if every email has your name on it and a reply from the right ten people matters more than a thousand sends. And on Studio you can keep Istos for the writing and approving and let Instantly do the sending.
How we checked
On 5 October 2026 we read each company's own pricing and product pages, linked below. We didn't use review sites or third-party lists. Prices are in US dollars as the pages showed them to us. Where a page didn't state something, the table says so. If you work at one of these companies and something here is wrong or out of date, email info@istosagent.com and we'll fix it.
Sources
- Apollo, Apollo.io pricing plans (opens in a new tab). Checked 5 Oct 2026.
- Clay, Clay pricing (opens in a new tab). Checked 5 Oct 2026.
- Clay, Clay home page (opens in a new tab). Checked 5 Oct 2026.
- Instantly, Instantly pricing (opens in a new tab). Checked 5 Oct 2026.
- Istos Agent, Pricing. Checked 5 Oct 2026.
Let the agents do the searching
Istos is in private beta. Join early access, or try the free preview on your resume, your website or your raise first. Nothing sends until you approve it.
