Enterprise-class signing,built for agents.
Legacy e-signature tools were built for a human clicking through a portal. But SumoSign is an API your agent calls directly. It requests, routes, signs, and returns evidence — no human in the loop. No bloat from a tool that predates AI.
Claude · ChatGPT · Grok Bot · Hermes · OpenClaw · MCP · REST API
Who is SumoSign for?
Agentic
Your agent already writes the contract. Now it can send it, too. One API call and your agent gets a signature back. No portal, no manual step, no dropped thread.
Developers
Don't build e-signing into your product. Compliance, audit trails, legal validity, edge cases: it is a lot of surface area for something that is not your core product. Plug in one API and skip the years it took incumbents to get this right.
Deal Teams & Agencies
Your AI drafts the proposal and runs the follow-ups. When it is time to close, SumoSign handles the signature on infrastructure built to carry deals worth closing. Not a free tool bolted onto a workflow.
Clients notice when a signing flow feels cheap. SumoSign runs on the same class of infrastructure enterprise teams have trusted for years. When your agent sends a contract, it carries the weight of something built to close million-dollar deals, not a weekend integration.
The numbers behind the positioning.
Three states. One source of truth. Same workflow whether a human or an agent runs it.
Prepare
Template, brand, route. Your team or your agent handles missing signers and bounced emails without restarting the packet.
Sign
Anywhere, any device, with your branding. The signer never wonders whose product they just entered.
Prove
Evidence bundle, audit trail, API webhook. Everything structured for counsel, not screenshots.
Aggregate, route, and prove in one platform.
Legacy signing forces your deal into a vendor portal. SumoSign was built API-first so every capability works from the dashboard or a scoped key at the same fidelity.
Run multi-party signing
Parallel or sequential routing, CC viewers, reminders on your cadence, and one certificate when everyone is done. From the dashboard or the API.
Explore the productLook serious when they sign
Your logo, your colors, your sender name on every signing page and email. Recipients never wonder whose tool they just signed in.
See how we compareProve what happened
Append-only audit trail with actor attribution, certificate of completion, and a downloadable evidence bundle structured for counsel.
Read the security notesAutomate the workflow
Every dashboard action is available through scoped API keys and MCP. Agents prepare, route, send, and watch. Signing stays with people.
Explore the APIStop apologizing for your signing link.
Prepaid envelopes from $10. Your agent runs the workflow. Your client sees your brand.
Everything a contract-heavy team needs.
Looking for something else? Tell us what you'd automate first.
Book a demoYour agents run the workflow, not the signature.
These are the kinds of requests your team delegates to agents connected via MCP or scoped API keys. Signing stays with authorized people; the trail always shows who acted.
Send & route
“Send this NDA to jane@acme.com for signature”
Upload and send with your branding
“Send to alice@co.com, bob@co.com — bob signs first”
Multi-party with routing order
“Use our Standard MSA template for the new client”
Instantiate a saved template
Track & manage
“Has Jane signed the NDA yet?”
Check status of any envelope
“Brief me on all pending signatures”
Pending, overdue, and completed overview
“Download the fully executed agreement”
Signed PDF plus certificate
Configure
“Set reminders at 3, 7, and 14 days”
Automatic follow-up cadence
“Void the envelope — deal fell through”
Cancel in progress with audit entry
“Replace the signer — wrong email on the envelope”
Revoke token and reroute
At a glance
- Agent-native API and MCP: your agent prepares, sends, and tracks — every signature stays with a human recipient.
- Prepaid envelope packs from $10 with branded multi-party envelopes and court-ready audit evidence.
- Enterprise-grade infrastructure on AWS — custom domains, voice signing, and procurement-friendly rollout on committed Enterprise volume.
Your questions, answered like an operator would.
A SaaS e-signature API lets your product collect legally binding signatures inside your own app — branded signing pages, multi-party routing, webhooks, and exportable evidence — without building that stack yourself. SumoSign is that API: prepaid packs from $10, full REST, MCP, and llms.txt on every pack, and a two-credential model so an agent can send while only a human can sign.
SumoSign follows established e-sign frameworks (for example ESIGN and eIDAS-style evidence practices) used in regulated industries. Enforceability always depends on jurisdiction and document type; we concentrate on defensible signer identity, captured intent, and tamper-evident records your counsel can rely on.
Least-privilege roles, encryption in transit, scoped API and agent credentials, and append-only audit trails are table stakes for enterprise signing. Controls exist to support regulatory review and procurement questionnaires, not checkbox marketing.
Expect a direct cutover plan: map templates, recreate branding and domains, parallel-send a cohort, then shift volume. The goal is first-party signing without the enterprise procurement detour.
Custom domains (sign.yourcompany.com) are available on Enterprise plans. You add one CNAME, we verify DNS, and signing links and emails go out on your host with SSL issued automatically. Teams that control DNS typically provision in one session.
Yes. Voice-guided signing is available on Enterprise plans for teams that need accessible or hands-free signing ceremonies.
Agents draft from templates, place fields, route envelopes, poll status, call webhooks, and archive outcomes. Signing stays with people, or with explicitly authorized machine identities where the legal model is defined; agents do not impersonate signers. Delegation is never ambiguous in the trail: you always see who acted, under which credential, and when.
Yes — start with a 30-day free trial, no credit card required. You get up to 25 envelopes with full API, MCP, and llms.txt access; just verify your email to activate. No sales call, no card on file.
When your trial ends, sending pauses and your account switches to read-only — you keep full access to view, track, and download everything you've already sent, and your documents and audit trails are retained for 12 months. Buy a prepaid envelope pack any time to resume sending; leftover trial envelopes are not added to the pack. Nothing is deleted and nothing is billed automatically.
Prepaid packs, not a monthly subscription: $10 for 20 envelopes, $25 for 60, $100 for 320, $250 for 1,000 — one send is one envelope across dashboard, API, and agents. Lots expire after 12 months; unused remainder is not refundable. We email you when a lot runs low, and send pauses at zero until you buy another pack — never a surprise overage bill. Enterprise is a committed-volume invoice, not a self-serve pack.
Signing should make your company look serious.
Prepaid envelopes from $10. Connect your agent with one API key and send your first envelope today.