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REST API Reference

Base URL: https://api.opencapstack.com/api/v1
OpenAPI Spec: /openapi.json
Interactive Docs: /api-docs (Swagger UI)

All requests require:

Authorization: Bearer <token>
Content-Type: application/json

Authentication​

MethodEndpointDescription
POST/auth/registerCreate account, returns JWT
POST/auth/loginEmail/password login
POST/auth/ainative-loginAINative SSO login (server-side)
POST/auth/refreshRefresh JWT using refresh token
POST/agents/onboardZero-friction agent registration
GET/auth/meGet current user profile

Stakeholders​

Cap table participants — founders, investors, employees, advisors.

MethodEndpointDescription
GET/stakeholdersList all stakeholders
POST/stakeholdersCreate a stakeholder
GET/stakeholders/:idGet stakeholder by ID
PUT/stakeholders/:idUpdate stakeholder
DELETE/stakeholders/:idDelete stakeholder

Create a Stakeholder​

curl -X POST https://api.opencapstack.com/api/v1/stakeholders \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "Jane Doe",
    "email": "jane@startup.com",
    "type": "EMPLOYEE",
    "title": "CTO"
  }'

Stakeholder types: FOUNDER INVESTOR EMPLOYEE ADVISOR BOARD_MEMBER

Response:

{
  "id": "stakeholder_abc123",
  "name": "Jane Doe",
  "email": "jane@startup.com",
  "type": "EMPLOYEE",
  "title": "CTO",
  "companyId": "co_xyz789",
  "createdAt": "2026-05-13T00:00:00Z"
}

Share Classes​

MethodEndpointDescription
GET/share-classesList all share classes
POST/share-classesCreate a share class
GET/share-classes/:idGet share class by ID
PUT/share-classes/:idUpdate share class

Create a Share Class​

curl -X POST https://api.opencapstack.com/api/v1/share-classes \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "name": "Series A Preferred",
    "type": "PREFERRED",
    "totalShares": 10000000,
    "pricePerShare": 1.00,
    "liquidationPreference": 1.0,
    "conversionRatio": 1.0
  }'

Share class types: COMMON PREFERRED OPTIONS_POOL WARRANT

Equity Grants​

Stock options, RSUs, and warrants issued to stakeholders.

MethodEndpointDescription
GET/equity-grantsList all grants
POST/equity-grantsIssue a new grant
GET/equity-grants/:idGet grant by ID
PUT/equity-grants/:idUpdate grant
GET/equity-grants/:id/vestingGet vesting schedule

Issue an Equity Grant​

curl -X POST https://api.opencapstack.com/api/v1/equity-grants \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "stakeholderId": "stakeholder_abc123",
    "shareClassId": "sc_options_pool",
    "quantity": 100000,
    "grantType": "OPTION",
    "strikePrice": 0.10,
    "vestingSchedule": "4_YEAR_1_YEAR_CLIFF",
    "grantDate": "2026-05-13"
  }'

Grant types: OPTION RSU WARRANT RESTRICTED_STOCK

Vesting schedules: 4_YEAR_1_YEAR_CLIFF 3_YEAR_MONTHLY IMMEDIATE CUSTOM

Response:

{
  "id": "grant_def456",
  "grantNumber": "GRANT-MP34648T-FF2DB6F9",
  "stakeholderId": "stakeholder_abc123",
  "quantity": 100000,
  "grantType": "OPTION",
  "strikePrice": 0.10,
  "status": "PENDING",
  "vestingStartDate": "2026-05-13",
  "fullyVestedDate": "2030-05-13"
}

SAFE Notes​

Simple Agreements for Future Equity.

MethodEndpointDescription
GET/safesList all SAFEs
POST/safesCreate a SAFE
GET/safes/:idGet SAFE by ID
PUT/safes/:idUpdate SAFE

Create a SAFE​

curl -X POST https://api.opencapstack.com/api/v1/safes \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "investorId": "stakeholder_investor1",
    "investmentAmount": 500000,
    "valuationCap": 10000000,
    "discountRate": 0.20,
    "safeType": "POST_MONEY",
    "issueDate": "2026-05-13"
  }'

SAFE types: PRE_MONEY POST_MONEY MFN

409A Valuations​

MethodEndpointDescription
GET/valuationsList valuations
POST/valuationsRequest a new 409A valuation
GET/valuations/latestGet most recent valuation
GET/valuations/:idGet valuation by ID

Request a Valuation​

curl -X POST https://api.opencapstack.com/api/v1/valuations \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "valuationDate": "2026-05-13",
    "methodology": "INCOME_APPROACH",
    "notes": "Pre-Series A valuation"
  }'

Cap Table​

MethodEndpointDescription
GET/cap-tableFull cap table summary
GET/cap-table/fully-dilutedFully diluted share count
POST/cap-table/dilutionModel dilution for a new round
POST/cap-table/waterfallRun liquidation waterfall analysis

Cap Table Summary​

curl https://api.opencapstack.com/api/v1/cap-table \
  -H "Authorization: Bearer $TOKEN"

Response:

{
  "companyId": "co_xyz789",
  "asOfDate": "2026-05-13",
  "totalAuthorizedShares": 20000000,
  "totalIssuedShares": 12500000,
  "fullyDilutedShares": 14000000,
  "shareClasses": [
    {
      "name": "Common Stock",
      "shares": 8000000,
      "ownership": 0.571
    },
    {
      "name": "Series A Preferred",
      "shares": 4500000,
      "ownership": 0.321
    }
  ],
  "topStakeholders": [
    { "name": "Jane Doe (Founder)", "shares": 5000000, "ownership": 0.357 },
    { "name": "Acme Ventures", "shares": 4500000, "ownership": 0.321 }
  ]
}

Dilution Modeling​

curl -X POST https://api.opencapstack.com/api/v1/cap-table/dilution \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "roundSize": 5000000,
    "preMoneyValuation": 20000000,
    "newShareClassName": "Series B Preferred"
  }'

Documents​

MethodEndpointDescription
GET/documentsList documents
POST/documentsUpload a document
GET/documents/:idGet document metadata
GET/documents/:id/downloadDownload document
DELETE/documents/:idDelete document

Upload a Document​

curl -X POST https://api.opencapstack.com/api/v1/documents \
  -H "Authorization: Bearer $TOKEN" \
  -F "file=@grant_agreement.pdf" \
  -F "type=GRANT_AGREEMENT" \
  -F "stakeholderId=stakeholder_abc123" \
  -F "grantId=grant_def456"

Financial Reports​

MethodEndpointDescription
GET/financial-reportsList reports
POST/financial-reportsGenerate a report
GET/financial-reports/:idGet report

Generate an Investor Report​

curl -X POST https://api.opencapstack.com/api/v1/financial-reports \
  -H "Authorization: Bearer $TOKEN" \
  -H "Content-Type: application/json" \
  -d '{
    "type": "INVESTOR_UPDATE",
    "format": "json",
    "asOfDate": "2026-05-13"
  }'

Report types: INVESTOR_UPDATE CAP_TABLE_SUMMARY EQUITY_LEDGER TAX_SUMMARY AUDIT_READY

Pagination​

All list endpoints support cursor-based pagination:

GET /api/v1/stakeholders?page=1&limit=50

Response envelope:

{
  "data": [...],
  "pagination": {
    "page": 1,
    "limit": 50,
    "total": 142,
    "hasMore": true
  }
}

Error Codes​

StatusCodeMeaning
400VALIDATION_ERRORInvalid request body
401UNAUTHORIZEDMissing or expired token
403FORBIDDENValid token but insufficient scope
404NOT_FOUNDResource does not exist
409CONFLICTDuplicate resource (e.g. same email)
429RATE_LIMITEDToo many requests — see rate limits
500INTERNAL_ERRORServer error

Error response shape:

{
  "error": "VALIDATION_ERROR",
  "message": "stakeholderId is required",
  "field": "stakeholderId",
  "statusCode": 400
}

Rate Limits​

PlanAPI calls/monthBurst
Free1,00010/min
Starter10,00060/min
Professional100,000300/min
EnterpriseUnlimited1,000/min

Rate limit headers are included on every response:

X-RateLimit-Limit: 60
X-RateLimit-Remaining: 47
X-RateLimit-Reset: 1715000000