How To API Contract With The Atlas API
---
title: How To API Contract With The Atlas API
description: How To API Contract With The Atlas API: POST /api/envelope, review URL, webhooks, and five free sends to test the flow. Upload PDF or DOCX, open review, send when re
date: 2026-06-08
updated: 2026-06-23
author: Atlas Team
primary_keyword: api contract
kd: 5
volume: 610
traffic_potential: 610
conversion_weight: 1.4
primary_cta: /docs/guides/e-signature-api
expected_conversion: read_then_signup
pov_lens: mcp-not-wrapper
phase: E
tier: 1
archetype: api-recipe
cluster_id: api-esign-core
cover_image: /blog/og/esign-core
---
Someone asked how to "API contract" as a verb. They meant send a real agreement from code, not read a glossary.
Share: "Upload, review, send. That is the loop."
Contract send from code
POST /api/envelope accepts PDF or DOCX via JSON document_url or multipart upload. Response includes envelope_id and review_url.
curl -X POST https://atlaswork.ai/api/envelope \
-H "Authorization: Bearer $ATLAS_API_KEY" \
-H "Content-Type: application/json" \
-H "Idempotency-Key: api-contract-1" \
-d '{
"document_url": "https://example.com/msa.pdf",
"parties": [{"email": "signer@example.com", "name": "Signer", "role": "Customer"}]
}'
Open review, confirm fields, send. One credit per send. Drafts are free.
Webhooks and CRM updates
Set webhook_url on create. Verify X-Atlas-Signature before updating deal stage in your CRM.
Templates after legal approval
Save a trusted shape as a template. Repeat sends can auto-send when counsel signs off on the layout.
Error codes
402 credits exhausted. 409 fields pending or version mismatch. Log envelope_id on every create.
MCP alternative
Agents can call ten MCP tools at /API/MCP when you want signing inside Claude or ChatGPT threads.
Sequential signing
Multi-party deals sign in order. Each sign_url needs ?t=<token>. See sequential signing.
Testing path
Send one envelope to yourself. Sign on mobile. Confirm webhook and signed PDF before production traffic.
curl -X POST https://atlaswork.ai/api/envelope \
-H "Authorization: Bearer $ATLAS_API_KEY" \
-H "Content-Type: application/json" \
-H "Idempotency-Key: esigncore-1" \
-d '{"document_url":"https://example.com/agreement.pdf","parties":[{"email":"you@company.com","name":"You","role":"Customer"}]}'
Open review_url before send.
Takeaway
Run one real envelope to yourself this week. Sign on your phone. Confirm webhooks before production traffic. Then read the API docs for full wiring.
If sends start in code or agents and you want review before email, Atlas is built for that shape.
See the comparison hub for full tables.
FAQ
Does Atlas accept PDF and DOCX?
Yes. DOCX becomes PDF before anyone signs.
How do I authenticate API calls?
Bearer API key from dashboard settings. MCP uses OAuth in ChatGPT and Claude.
One question for you
What broke last time you tried to wire signing into your stack?
Related reading
DocuSign honest take
DocuSign works for one-off agreements someone uploads in a browser. It hurts when every send is API or MCP and you pay per seat for service accounts.
Parallel-run Atlas on one workflow before you cancel a renewal. Template rewrite costs more than route mapping.
Webhooks and status
Set webhook_url on create. Verify X-Atlas-Signature with your API key before you update CRM or billing state.
Handle envelope.sent, envelope.signed, envelope.declined, and envelope.voided. Log envelope_id on every create.
Retry safety
Send Idempotency-Key on create and send. Retries from cron jobs or agents return the first envelope instead of double-charging.
402 means out of credits. 409 often means fields still processing. Open review_url and read the banner.
Sequential signing
Party one signs first. Party two gets email after. Each signer needs sign_url with ?t=<token> on multi-party deals.
See sequential signing.
Pilot checklist
Week one: one document type, internal signers, webhook to staging. Week two: one external signer with real terms.
Compare signed PDF output with counsel before you widen scope. Five free sends on signup cover the pilot.
Pilot note
Run the same PDF through staging. Measure hours from create to signed file. Compare webhook delay and signed PDF layout before you pick a vendor for production traffic.
Support habits
When a signer stalls, remind instead of creating a duplicate envelope. When terms change, void pending and recreate with a fresh Idempotency-Key.
Metrics that matter
Track median hours from verbal yes to signed PDF. That number convinces finance faster than feature grids.
Security habits
Create envelopes from servers you control. Never put API keys in frontend bundles or public chat logs.
Pilot note
Run the same PDF through staging. Measure hours from create to signed file. Compare webhook delay and signed PDF layout before you pick a vendor for production traffic.
Support habits
When a signer stalls, remind instead of creating a duplicate envelope. When terms change, void pending and recreate with a fresh Idempotency-Key.
Metrics that matter
Track median hours from verbal yes to signed PDF. That number convinces finance faster than feature grids.
Security habits
Create envelopes from servers you control. Never put API keys in frontend bundles or public chat logs.
Pilot note
Run the same PDF through staging. Measure hours from create to signed file. Compare webhook delay and signed PDF layout before you pick a vendor for production traffic.
Support habits
When a signer stalls, remind instead of creating a duplicate envelope. When terms change, void pending and recreate with a fresh Idempotency-Key.
Metrics that matter
Track median hours from verbal yes to signed PDF. That number convinces finance faster than feature grids.