Docusign

DocuSign dominates e-signatures and the API reflects its maturity. For agents, the primary use case is programmatic document sending: create an envelope (document + recipients + signing tabs), send it, and track completion status. The eSignature REST API covers envelope creation, template usage, recipient management, signing tab placement, and document retrieval. Templates enable agents to send standardized agreements by filling in recipient information and custom fields. Connect webhooks notify agents when envelopes change status (sent, delivered, completed, declined, voided). Embedded signing enables in-app signing experiences without email redirects. For agents managing contract workflows — sales agreements, onboarding paperwork, compliance documents — DocuSign's API is comprehensive. The main barrier: the OAuth complexity and the envelope/tab data model have a learning curve.

eSignature REST API at {base_path}/v2.1/accounts/{accountId}/envelopes. The data model centers on envelopes: each envelope contains documents, recipients (signers, CC, in-person signers), and tabs (signature, initial, date, text, checkbox, dropdown placed on documents). Envelope creation sends the composite of documents + routing + tab placement in a single API call. Templates pre-define document layout and tab positions — agents fill in recipient info and custom field values. Recipient routing order controls the signing sequence. Bulk send handles high-volume identical envelopes with recipient CSV. The API supports composite templates (merge multiple templates), conditional tabs, and custom fields. Connect webhooks deliver envelope status events to configured URLs. The API surface is large but well-organized around the envelope resource.

API errors return JSON with errorCode and message. Standard HTTP status codes. Rate limits: 1000 API calls per hour per account, 2000 for large accounts. Burst limit: 15 requests per 15 seconds per user. The rate limits are relevant for agents processing many envelopes — bulk operations should use the bulk send API. Envelope status transitions (created → sent → delivered → completed/declined/voided) are well-defined with webhook notifications at each stage. Voided envelopes can include reasons. Expired envelopes (signing deadline passed) transition to 'voided'. The main error agents encounter: recipient validation failures (invalid email, duplicate recipients) return specific error codes. Tab validation errors (invalid position, conflicting tab types) also have specific codes. The sandbox environment enables full API testing without sending real envelopes.

Three OAuth flows: Authorization Code (interactive user consent), Implicit (browser-based), and JWT Grant (server-to-server for agents). JWT Grant is the recommended path for autonomous agents: create an integration key and RSA key pair in the DocuSign admin, exchange a JWT assertion for an access token without user interaction. The user must grant consent once via a consent URL, after which the agent can obtain tokens non-interactively. Access tokens expire in 1 hour and must be refreshed via new JWT assertion. Scopes include signature (eSignature operations), extended (additional access), and impersonation (act as other users). The organization admin must approve the integration. For agents, the JWT Grant flow is well-suited but the initial consent + admin approval setup adds onboarding steps.

Developer documentation at developers.docusign.com is extensive — tutorials, API reference, SDK documentation, and code examples. The API reference is generated from OpenAPI with try-it-out functionality. Quick start guides cover the most common flows: sending an envelope, using templates, embedded signing. SDKs are available for C#, Java, Node.js, PHP, Python, and Ruby — all official and well-maintained. The Developer Center includes a Postman collection. Sandbox accounts are free for development. The documentation's main challenge: the API surface is large and some features (conditional tabs, PowerForms, bulk send) require navigating deeper into the docs. For agents, the 'Send an Envelope' tutorial and JWT Grant authentication guide are the essential starting points.