Form backends have a structure problem.

Postbox is structured data collection for the agentic web. Define your schema, get an endpoint where submissions arrive validated, spam-filtered, translated and auto-replied.

New submission /f/feedback
name María García
email maria@acme.co
message Me encanta el nuevo diseño. ¿Cuándo estará disponible el plan Pro?
validated spam-checked spam caught translated reply drafted
ES → EN · "I love the new design. When will the Pro plan be available?"
How it works

Three steps. All conversation.

01

Connect.

Install the Postbox Skill, or connect the MCP server. One-time setup. Your agent now knows how to create and manage forms on its own.

setup
Skill MCP

          
Connected
02

Describe.

"Add a waitlist form." That's the whole brief. Your agent defines the schema, generates the UI, and wires up the endpoint — all in one go.

agent
03

Listen.

Submissions land in one inbox. The contract holds for any source — form, tool, or agent.

receiving
acme.com/feedback
Product feedback
name
feedback
rating
Submit
Feedback
name
feedback
rating
Submit
What's the feedback looking like?
👤
🤖
12 so far, average 4.2. Three said export is slow. Two want mobile dark mode. One 1-star on settings. The rest are compliments on the new design.
What you'd have built yourself

Only you didn't have to.

Validated

Bad data never lands.

You define the schema. Postbox enforces it at the endpoint — types, required fields, patterns, ranges. Per-field errors come back structured.

POST /f/contact
name: "Alice",
email: "not-an-email",
rating: 5
422 { email: ["must be a valid email"] }
Spam-filtered

Spam never makes it to your inbox.

Free heuristics out of the box. Flip on AI for spam that understands your form's intent — the junk that passes keyword filters but obviously doesn't belong.

Sarah — Interested in your Pro plan clean
FREE CRYPTO!!! Claim $5000 now spam
James — Discount for nonprofits? clean
Translated

Every language, one inbox.

Auto-detected and translated on the way in. The original is always kept — nothing lost in translation, nothing waiting for you to decode.

Original · Spanish
Me encanta el nuevo diseño. ¿Cuándo estará el plan Pro?
Translated · English
I love the new design. When will the Pro plan be available?
Reply drafted

Questions answer themselves.

Point at a knowledge base. Postbox drafts a reply for every submission — or sends it on your behalf. The stuff you'd answer the same way every time, you stop answering.

Do you offer a discount for nonprofits?
sent · from knowledge base
Yes — we offer 50% off for registered nonprofits. Send your 501(c)(3) documentation and we'll apply the discount to your account.
How data flows in

Your agent already knows how to wire this up.

Skill

Inside your codebase.

Drop the Postbox Skill into your project once. From then on, your coding agent knows how to create forms, wire the endpoint, and drop the snippet into your UI — while it's shipping the rest of the feature.

terminal ⎘ copy
$ npx skills add https://github.com/variant-systems/skills --skill postbox
then tell your agent: "Add a waitlist form to the landing page" "Show me today's submissions" "Forward the contact form to Slack"
MCP

Inside your chat.

Point any MCP-aware client — Claude, Cursor, your personal agent — at the Postbox server. Create forms, inspect submissions, change destinations. Without leaving the conversation.

mcp.json ⎘ copy
{
  "mcpServers": {
    "postbox": {
      "type": "http",
      "url": "https://usepostbox.com/mcp"
    }
  }
}

Or just click through the dashboard.

The dashboard does everything the agent does. Fine for handing off to a client, or when you just want to poke around.

Inside the foundation

Every submission flows through this pipeline.

Validate, spam check, translate, reply, notify — configurable per form. Submitters always get 201 instantly; everything else happens async.

postbox pipeline
processing...
Form settings
Spam protection standard
Translation off
Smart replies off
Destinations
incoming submission
POST /api/.../f/contact
Validate
Spam
Translate
Reply
Notify
What you're probably building

One of these, most likely.

Marketing & Sales

Make a lasting first impression.

The forms that turn strangers into a list, and a list into a conversation. Waitlists that build anticipation, lead capture that routes straight to your CRM, demo requests that schedule themselves. Built for speed, volume, and the exact moment someone decides they are interested. Validation keeps garbage out. Spam filtering keeps noise down. Your pipeline stays clean from the first touch.

Waitlist Lead capture Newsletter Demo request Event signup
Join the waitlist
alex@futurecorp.io
How did you hear?
Reserve your spot
2,847 already in line
Support

Most questions answer themselves.

Plug in your knowledge base and suddenly every submission gets a thoughtful, contextual response. Postbox drafts replies from your docs — or sends them on your behalf if you trust the match. Contact forms, bug reports, feature requests, refund inquiries. The questions you would answer the same way every time, you no longer answer at all. Your support team handles the edge cases while Postbox handles the routine.

Contact Support tickets Bug reports Feature requests Feedback
james@northwind.dev · 2m ago
Hey — do you offer a discount for nonprofits? We're a small 501(c)(3).
replied · from knowledge base
Yes — we offer 50% off for registered nonprofits. Send your 501(c)(3) documentation to support@usepostbox.com and we'll apply the discount to your account.
Operations

The forms that run the process.

When the form isn't the goal — it's a step in something bigger. Vendor onboarding that triggers compliance checks. Internal requests that route to the right team. RSVPs that update headcount automatically. Structured input that drives a workflow instead of creating another spreadsheet to maintain. Every field maps to an action downstream, so data flows instead of piling up.

Vendor onboarding RSVPs Internal requests Intake forms Approvals
company Northwind Logistics new
contact maya@northwind.co
service Freight forwarding
starts May 1, 2026 pending
Research

Surveys without the spreadsheet.

Surveys and polls that turn into structured data the moment they're submitted. User research that segments itself. Beta feedback that surfaces themes without manual tagging. Pricing studies that compare responses across cohorts. No spreadsheet wrangling, no copy-paste, no pivot tables — the answers arrive ready to read, filter, and act on. Your agent can even summarize patterns and draft follow-up questions from the same dataset.

Surveys User research Polls Beta feedback Pricing studies
What did people want most?
👤
🤖
used postbox.query_submissions
Webhooks v2 — 78% of respondents. Especially common from teams over 10 people.
Anyone unhappy with pricing?
👤
🤖
7 mentions. Mostly free-tier users hitting the 5,000 submission cap.
Going beyond

The lads at the lab are always up to something.

Experiments from the edge of what data collection can be when agents are part of the loop.

Agent → Agent

The RSVP that ran itself.

We wired one agent to plan a dinner for thirty. It created the form on Postbox and sent the endpoint to everyone else's agents. RSVPs flowed in structured — dietary prefs, plus-ones, confirmations. Nobody opened a browser.

Phase 1 · Organiser's agent broadcasts
🤖
Alice, Bob, Carol, Dave via Telegram
"Dinner Friday 7pm — RSVP here: usepostbox.com/.../f/dinner-rsvp"
+ 26 others
Phase 2 · Agents respond via Postbox
A
Alice's agent attending · vegetarian, +1
B
Bob's agent attending · no dietary, +0
C
Carol's agent maybe · gluten-free, +1
D
Dave's agent attending · vegan, +2
+
24 more responses…
28/30 confirmed · 5 vegetarian · 8 plus-ones · 0 browsers opened
Human → Agent

One prompt. Fully wired.

"I need a contact form on the website." That's the whole brief. The agent creates the schema on Postbox, builds the UI, connects the endpoint, and deploys — all in one shot.

I need a contact form on the website.
👤
🤖
postbox.create_form
postbox.add_fields
connect_endpoint
deploy_changes
🤖
Done. Here's what I deployed:
Contact us
Send
Live at /contact — posting to Postbox with validation, spam filtering, and email notifications.
Pricing

The free plan isn't a trial.

Free
$0
Free forever
  • 1 form
  • 5,000 lifetime submissions
  • 50 AI credits (one-time)
Start for free
Pro
$19/ month
For when you outgrow free
  • Unlimited forms
  • Unlimited submissions
  • Webhooks, Discord, and Slack destinations
  • 500 AI credits per month, replenishing
  • Pay as you go after credits run out
  • Priority support
Go Pro
FAQ

The questions we keep getting.

What happens when I hit the 5,000 submission cap? +
Postbox returns a 429 to the next submitter with an upgrade link. Your existing data stays put. Upgrading to Pro lifts the cap immediately and removes the form limit too.
Do you support file uploads? +
Not yet. Postbox handles structured data — strings, numbers, dates, booleans, emails — with rule-based validation. File uploads are on the roadmap. If you need them today, Postbox isn't the right fit.
How do I get submissions into my own systems? +
Set up a destination on the form. Postbox supports webhooks with HMAC signing, Discord, and Slack. Available on Pro.
Can I export my submissions if I leave? +
Yes. Reach out to support and we'll give you full access to your data — every submission, every schema version. Your data is yours.
Does Postbox work with my framework? +
If it can make an HTTP request, it works. There's no SDK to install. You POST JSON to your form's endpoint, and Postbox returns structured per-field validation errors you can show inline — works the same in React, Vue, Svelte, Next, Remix, plain HTML, or anything else.
What if I need to change a form's schema later? +
Change it whenever you want. Every schema update creates a new endpoint URL — Postbox returns it in the API response. The old URL keeps working forever, validating against the schema it was created for. Your website can adopt the new schema while your mobile app stays on the old one. Nothing breaks.
Can my non-technical client manage forms themselves? +
Yes. The dashboard handles everything — creating forms, editing fields, reading submissions, configuring destinations, replying to inbound. No code, no API knowledge needed. Hand it off and walk away.
How is this different from Typeform or Google Forms? +
Typeform and Google Forms are built for humans filling out pretty UIs. Postbox is built for agents and developers who need a contract-first approach. You define a schema and get an API endpoint. Agents can create, read, and manage forms through MCP or skills. Submissions are validated at the edge, spam-filtered, translated, and routed to your systems automatically. It's the difference between a survey tool and infrastructure.
What does "agent-native" actually mean? +
It means your AI assistant can interact with Postbox directly. Through our MCP server, Claude, Cursor, or any MCP client can list your forms, inspect submissions, summarize feedback, and draft replies — all through natural conversation. Through our Skill, coding agents like Claude Code can create forms, wire endpoints, and manage destinations from your terminal. You never have to leave your workflow to handle form data.
Is there a limit on how many submissions I can receive? +
Free plan includes 5,000 lifetime submissions across all your forms. Pro is unlimited. We have customers processing tens of thousands a month without issue. If you're expecting truly massive volume, reach out — we can discuss dedicated infrastructure.
How does the spam filtering work? +
Two layers. First, standard heuristics: honeypot fields, rate limiting, known bot signatures, and suspicious patterns. This catches the obvious stuff and costs nothing. Second, AI-powered spam detection that understands the intent of your specific form. A crypto pitch on a contact form gets flagged even if it passes keyword filters. You choose which layer to enable per form. Caught spam is quarantined, not deleted, so you can review false positives.
Internal security audit — April 2026. Zero critical findings.
TLS everywhere. Encrypted sessions. Data isolation guarantees upheld.
read the report →
Say hi

This form runs on Postbox.

Built with the same Skill you'll install. Every message hits our live endpoint — validated, spam-checked, and in our inbox before you close the tab.

live postbox endpoint
POST /f/say-hi