The agent already picked the next step. Update the Salesforce lead. Pull the Slack thread. Close the HubSpot deal. Then it hit a 401. No per-tenant OAuth. No tool schema it could discover at runtime. Someone on the team was supposed to paste a refresh token into a .env and hope Claude still knew the verb.
That hole is the category. G2 minted it in July 2026 as AI Integration Tools Platforms: the agent is the client, it finds an action at runtime, and the platform holds credentials, rate limits, and retries. Four AI agent integration platforms we would actually shortlist: StackOne, Paragon, Nango, and Composio.
We read first-party product pages, one AWS Marketplace listing, and dated changelogs this week. Catalog counts on those pages are vendor claims. We did not count connectors, and we did not run the OAuth flows.
Someone on HN already had the kill question:
"Ok, how do we do customer auth" has become my go-to question to kill MCP projects. There is no working solution which makes any kind of enterprise exploration into the space pointless.
These four exist to take that question off the whiteboard.
The other half of the hole is context, not login. Mario Zechner walked a Drive transcript into a Salesforce lead and watched the full text pass through the model twice — another 50,000 tokens on a two-hour meeting if every intermediate result has to live in the prompt. That is why the interesting surface here is tool search, not dumping the whole catalog into the system prompt.
StackOne
StackOne is the agent-native pole of this list: one MCP, A2A, or REST front door over a SaaS action catalog, plus tool search, human-in-the-loop Agent Auth, and StackOne Defender. Romain Sestier and Guillaume Lebedel founded it in London in 2023. The Series A was $20 million on 6 May 2025, led by GV, with Workday Ventures, XTX Ventures, Episode 1, and Playfair. Tracxn later prints a ~$24.4 million total; that figure is third-party, not the company post.
The catalog marketing does not agree with itself. The homepage we fetched says 450+ integrations and 28,000+ tools. The MCP product page says 479 MCP servers and 28,928 tools. The pricing page says 450+ and 29,000+. Vendor-claim, and the three URLs disagree — we are not averaging them.
Two motions sit on that catalog. Gateway is for a team running its own agents. OEM is white-label for a SaaS product embedding integrations for its tenants. Auth is a basic API key plus x-account-id, or a per-account token URL. MCP OAuth shipped on 7 Aug 2026.
Best for:
A first-party agent team that needs runtime tool search and A2A, or a SaaS product that wants the same catalog white-labeled, and that will read the credit math before the POC.
Key Features:
- A single MCP at
https://api.stackone.com/mcp, or a per-connector/rpc/{connector}/mcp, plus first-party A2A — the only one of these four with A2A docs. - Search & Execute: the model looks up a tool instead of loading the whole catalog into context.
- Agent Auth for human consent on writes; Defender (company says the core is open-source, plus Premium) for runtime checks.
- Falcon as an MCP client, an AI Connector Builder, and the older unified HRIS/ATS APIs still in the docs.
Why we like it:
This is the cleanest "the agent is the caller" page. Search & Execute is the product answer to Zechner's Drive-to-Salesforce loop. The changelog is dated, which the others mostly are not: MCP tool annotations on 24 Jul, a docs re-org on 3 Aug, OAuth on 7 Aug.
Notable Limitations:
- Credit math is easy to undercount. Search plus execute can be two calls, and the vendor says 1 credit ≈ 1 tool call.
- The $600/mo Gateway Team card does not print a seat floor we can defend.
- Unified-API heritage is still on the site. Some buyers will read it as a Merge-class HRIS sync and miss the agent surface.
- No AWS Marketplace listing this week.
Pricing:
Public for Gateway Team; quote for Enterprise and OEM Enterprise. Gateway Starter is $0 with 1,000 credits per seat per month; extra credits $60 per 20k. Gateway Team is $600/mo; extra credits $20 per 20k. OEM Core is $0 for 2 accounts and 500 credits per account per month. Enterprise and OEM Enterprise are sales calls.
Paragon
Paragon is embedded integration infrastructure that grew an agent surface on top of a mature Connect Portal. Brandon Foo and Ishmael Samuel founded it in 2019 in Los Angeles, not San Francisco. Inspired Capital led a $13 million Series A on 27 Jul 2022; the company said $16.5 million total at the time. We found no AI-era round through this week. The Series A blog still on the site carries a 25 Jul 2026 CMS stamp. That is a re-publish, not a 2026 raise.
Workflows is the old embedded iPaaS. ActionKit is the agent layer: an API and an MCP for tools, plus triggers. The product still talks 130+ integrations and 1,000+ actions. Vendor-claim, dated on the MCP page (31 Jul 2026) and the ActionKit page (11 Aug 2026). No A2A.
Auth is managed OAuth 2.0 and API keys per Connected User — a customer org, not a seat. The Connect Portal can be embedded or headless. A JWT user token (RS256) goes from the product to Paragon; a magic-link fires when the end user is not connected yet. Custom actions come from OpenAPI. Enterprise can self-host or forward-deploy.
Best for:
A B2B or AI SaaS product that already thinks in Connected Users and wants agents to share the same per-tenant OAuth as the existing embedded integrations.
Key Features:
- Hosted ActionKit MCP, and an MIT MCP adapter over the same API. The platform behind it is closed.
- ActionKit Triggers, launched 14 Aug 2026: an agent can subscribe to Slack, HubSpot, or Salesforce events instead of only firing writes.
- Connect Portal for per-tenant OAuth, including multi-account auth and bring-your-own client on some apps.
- Managed Sync and Workflows still ship on the same auth layer. Do not pretend the iPaaS surface is gone.
Why we like it:
The agent features sit on an auth runtime that was already built for other people's customers. Triggers (14 Aug) are the dated ship in the window. If your buyer is "our SaaS embeds Salesforce for our tenants, and now the agent has to use that connection," this is the motion.
Notable Limitations:
- Pricing is quote-only. The pricing page has Pro vs Enterprise and a trial CTA. No dollars. No public free plan. Competitor teardowns exist; they are not a price list.
- No AWS Marketplace listing for useparagon / ActionKit this week. Unrelated "Paragon Cloud Services" listings are a different company.
- Closed platform except the thin MIT adapter. No A2A.
- Ry Walker’s 2026 research treats the app catalog as smaller than Nango or Composio if you count providers, not actions. We did not count either.
Pricing:
Quote-only. Meter is Connected Users. Enterprise adds self-host, SAML SSO, HIPAA, and SLAs. G2's product card showing Pro as a $0 free trial is a trial badge, not a list price.
Nango
Nango is the code-first pole. You — or a coding agent — write TypeScript functions. Nango runs auth, execution, syncs, and webhooks, then exposes those actions over REST or a hosted MCP. Robin Guldener and Bastien Beurier started the company in 2022 (YC W23); the product story often says 2023. San Francisco, 156 2nd Street.
Gradient announced a $7.5 million seed on 23 Mar 2026. Nango's own related-posts widget later dates the same post 1 Apr 2026. Horizon, Y Combinator, and angels including Akshay Kothari (Notion) and John Kim (Sendbird) participated. PitchBook also lists a 2023 seed and a Dec 2022 YC $500K. A PitchBook "raised $10 million" line is not something we can confirm; use the $7.5 million plus the earlier YC/seed.
The homepage claims 900+ APIs and 6,000+ templates. Nango's own competitor table elsewhere has said 5,000+ tools. Vendor-claim, and we are not reconciling those into one number. The catalog is "APIs you auth plus functions you write," not a giant pre-built tool dump. Nango argues that is the point.
Best for:
Engineering teams that will write the actions in TypeScript, want a $0 cloud plan or a self-hosted runtime, and do not need a visual Zap builder.
Key Features:
- Hosted MCP at
https://api.nango.dev/mcp(Streamable HTTP;Authorization,connection-id,provider-config-key). Runtime discovery viaGET /scripts/config. - A Management MCP (beta) at
https://mcp.nango.dev/mcpfor logs, plus CIMD and dynamic client registration for connecting users to other MCP servers. - White-label Connect UI, per-connection OAuth / API keys / refresh, and a Function Builder skill for Claude, Cursor, and Codex.
- Self-host under Elastic License 2.0. Source-available, not OSI Apache. Do not write "fully open source" on a purchase order.
Why we like it:
It is the only one of the four you can start at $0 and read as code. Dated GitHub releases landed in the window: v0.71.2 on 21 Jul (control-plane MCP, CIMD, log tools) and v0.71.4 on 10 Aug (integrations CRUD, self-hosted Management MCP). The cloud changelog is mostly undated, so we used the tags.
Notable Limitations:
- Smaller disclosed checkbook than StackOne or Composio.
- Syncs are migrating to Lambda with a 10-minute cap. The note is in the 2026 changelog; the exact day is not printed.
- No A2A. No AWS Marketplace listing this week.
- G2 and PeerSpot reviews were not fetched (timeouts).
Pricing:
Public. Free $0. Starter from $50/mo. Growth from $500/mo. Enterprise custom. An end-user connection is one billed connection: $1 each after the included bundle. Other overages print at $0.0001 per proxy request, function run, sync record, or webhook; $0.0000002 per ms of function compute; $0.00001 per custom log. Included volume: Free 10 connections and 100k of most meters; Starter 20 / 200k; Growth 100 / 1M.
Composio
Composio is a session-scoped tool catalog. You create a session for a user, get a managed MCP URL plus meta-tools (search, authenticate, execute), and run tools with Composio-managed OAuth. Soham Ganatra and Karan Vaidya founded it in 2023 in San Francisco.
Funding copy does not agree with itself. The company Series A post (22 Jul 2025) says $29 million. Page meta and some recaps say a $25 million Series A. Tracxn dates a Lightspeed Series A to 25 Mar 2025. Call it a $25 million Series A / $29 million total, per the company blog, and leave the two headlines sitting next to each other.
The catalog copy disagrees too. First-party marketing says 1,000+ toolkits. The AWS Marketplace listing still says 250+ tools. Both pages were live this week. Vendor-claim, and the two surfaces are not the same number.
No A2A. Legacy per-app MCP servers were migrated in Jun 2026; mcp.composio.dev was removed on 25 Mar 2026.
Best for:
Teams that want a per-user MCP URL and meta-tools, a public tool-call price card, and are willing to ignore the stale AWS SKU table.
Key Features:
composio.create(user_id)returnssession.mcp.url. The how-it-works doc is the cleanest first-party picture of the session model.- Meta-tools for search, auth, and execute — same "do not dump the catalog into context" idea as StackOne Search & Execute.
- Composio-managed OAuth apps, or bring-your-own. Self-managed credentials are listed as Included on the 15 Aug 2026 first-party table.
- A sandbox for untrusted tool code. SDKs are public; the platform is closed.
Why we like it:
It is the only one of the four with both a public first-party reprice inside the last 30 days (15 Aug 2026) and an AWS listing. The changelog is dated: OAuth callback hardening on 30 Jul, CLI work on 31 Jul and 5 Aug, free-form tool arguments on 6 Aug, SDK updates on 7 Aug.
Notable Limitations:
- Catalog (1,000+ vs 250+) and funding ($25 million vs $29 million) disagree across first-party and AWS copy.
- AWS prices and meters look older than the 15 Aug site. Prefer the site.
- G2 blurbs on the AWS card date from Dec 2024–Apr 2025.
- No A2A. Hard cap on the Free plan (100k tool calls, 50k triggers, 3 members).
Pricing:
First-party, for signups on or after 15 Aug 2026: Free $0, hard-capped. Pro $29/mo plus a $29 usage credit, then $0.0003 per tool call and $0.003 per trigger. Grandfathered customers keep the old card through 31 Dec 2026. Premium tools start billing everyone on 1 Sep 2026. AWS still shows Starter $29/mo (500 users, 100k API calls) and Growth $229/mo (3,000 users, 600k API calls). Those SKUs do not match the site.
Not a Zap, not a gateway, not a harness
Three ways to reach Salesforce
If a human is drawing the flow at design time, you are in iPaaS — Workato, Zapier, Tray, Boomi, MuleSoft already live on our iPaaS tools page, last updated 28 Apr 2026. None of the four above are on it. If you are routing and observing LLM calls, that is an AI gateway (28 Apr 2026): Portkey, Helicone, LiteLLM, TrueFoundry. A gateway does not log into Salesforce. If you need policy, eval, and identity over how an agent runs, that is an agent infrastructure or harness and guardrail buy, not a connector catalog.
In the same neighborhood, and not on this shortlist: Arcade if the hole is regulated auth (URL Elicitation, per-user scopes) rather than a large first-party catalog; Zapier MCP if you already live in Zapier and want a wrapper, not a new aisle; Merge if you are still normalizing HR/CRM reads for a B2B product and MCP is an extra surface. First-party Salesforce / Slack / HubSpot MCPs are vendor-specific. They are not a multi-app layer.
Is this iPaaS or an AI gateway?
iPaaS is a person configuring a workflow before anything runs. An AI gateway is a proxy in front of model traffic. This category is the other direction: the agent discovers a tool schema at runtime, the platform holds OAuth for a customer org or a connected user, and production retries sit on that call. If the demo opens on a canvas, you are in iPaaS. If it opens on a model picker and a latency graph, you are in a gateway. If it opens on a Connect Portal and a tool the model can search, you are in the right aisle.
One real fork on the cards: StackOne Gateway vs StackOne OEM is two quotes on one catalog. Gateway is per-seat for a team running its own agents. OEM is white-label for a SaaS product embedding integrations for its tenants. Mixing them is how you buy the wrong SKU. Paragon will not help you self-serve out of that fork — Connected Users, Pro vs Enterprise, no dollars on the page.
What the public cards meter
List prices as of 18 Aug 2026. The units are not interchangeable. Paragon stays quote-only. Composio numbers below are the first-party 15 Aug card, not the older AWS SKUs.
| Platform | Public list | Meter |
|---|---|---|
| StackOne | Gateway Starter $0 (1,000 credits/seat/mo); Gateway Team $600/mo (seat floor not printed); extra credits $60/20k on Starter, $20/20k on Team. OEM Core $0 (2 accounts, 500 credits/account/mo). Enterprise / OEM Enterprise quote. | Credits (vendor: 1 ≈ 1 tool call); seats on Gateway |
| Paragon | Quote-only. Pro vs Enterprise. Trial CTA, no free plan. | Connected Users (customer orgs) |
| Nango | Free $0; Starter from $50/mo; Growth from $500/mo; Enterprise custom. Overage $1/connection after the included bundle. | Connections + usage (requests, runs, compute, logs, sync records, webhooks) |
| Composio | Free $0, hard-capped (100k tool calls, 50k triggers, 3 members). Pro $29/mo + $29 usage credit, then $0.0003/tool call and $0.003/trigger. Grandfather through 31 Dec 2026. Premium tools bill from 1 Sep 2026. | Tool calls + triggers |
Bottom line
Pick the discovery and auth motion that matches the hole you can already name. "Our customers must connect their Salesforce to our agent" is a Connected User / OEM / per-connection buy. "The agent has to find one action without eating the context window" is Search & Execute, meta-tools, and a credit or tool-call meter. Those are different SKUs. A catalog number on a homepage is not a third option.
