Best of · Work & business apps
Best contract, proposal and e-signature APIs for AI agents
All 8 ranked contract, proposal and e-signature APIs on the Anchor benchmark, with a pick for each need and where each one falls short. Scores come from public evidence, re-checked as vendors change.
- 8 ranked
- 0 agent-ready
- 8 hosted endpoints
- Updated 9 October 2026
Top three
Picks by need
Worked out from the scores, prices and facts, so they change when the research does.
Maintenance & community
93/100 on maintenance & community, against 85 for the overall leader.
The shortlist
| # | Tool | Grade | Best for | Price | Where |
|---|---|---|---|---|---|
| 1 | Dropbox Sign Dropbox, Inc. |
B 68.9 | An agent that sends a prepared PDF or a saved template for signature from one company account and tracks it to completion by webhook or polling, with the signed PDF and audit trail at the end. | Paid | hosted |
| 2 | airSlate SignNow airSlate, Inc. |
B 68.5 | An agent that sends agreements from templates, embeds signing in another product or tracks invites, and teams that want per-invite pricing with a free test mode. | $2 / tx | hosted and local |
| 3 | PandaDoc PandaDoc |
B 63.1 | Suited to agents that prepare a proposal, quote or contract from a template, send it for signature and track it, for a team that already works in PandaDoc. | Freemium | hosted |
| 4 | Documenso Documenso, Inc. |
B 62.8 | Teams that want an e-signature API they can also self-host, with templates, embedded signing and an audit log by API. | Freemium | hosted |
| 5 | Docusign Docusign, Inc. |
B 62.5 | Teams whose company already uses Docusign and needs an agent to send envelopes from templates, embed signing and track status with a full audit trail. | $50 / mo | hosted |
| 6 | DocuSeal DocuSeal, LLC |
B 62.4 | A software company adding signing to its own product, paying per completed document, with HTML, PDF tag and DOCX variable templates and embeddable forms, and a choice of US or EU hosting or self-hosting. | $0.20 / tx | hosted |
| 7 | SignWell Docsketch, LLC (DBA SignWell) |
C 61.9 | A small software team adding signing to its own product at a per-document price with no seat minimum, embedded signing, requesting and template editing, and bulk send to 500 recipients. | $0.85 / tx | hosted and local |
| 8 | Adobe Acrobat Sign Adobe Inc. |
D 52.6 | A company that already holds Acrobat Sign Solutions and wants an agent to send agreements, track them by webhook and fetch signed files and audit trails. | $16.99 / seat-mo | hosted |
How to choose
- Field placement from templatesCheck that template fields land in the right place on the signed file, since an agent that fills fields by position needs them to stay fixed.
- Status events for each signerCheck which status events are sent for each signer and whether they arrive by webhook, since an agent needs them to know when a signature has landed.
- Audit trail in the signed fileCheck that the signed file carries an audit trail with signer identity and timestamps, since that record shows when each signature was made.
- Embedded signing in your productCheck whether signing can be embedded in your own product, since a redirect to an outside page breaks a flow an agent is driving.
How the benchmark tests this category. One agreement prepared from a template with the same fields, sent to two test signers and tracked to completion through each listing's API. We check field placement, the status events received, the signed file and its audit trail. In this run listings are graded from public evidence against the published checklist.
Each one in detail
Dropbox Sign
B 68.9/100Dropbox Sign (formerly HelloSign) is Dropbox's e-signature service. Its REST API sends documents or templates for signature, embeds signing in an iframe, reports status by webhook and returns signed PDFs with an audit trail.
Verdict A public OpenAPI 3.0.3 spec, llms.txt, six official SDKs and a free test mode let an agent build the whole flow before paying. Production sends need a paid plan from $900 a year, the API key has full account access, and no idempotency keys were found in the reviewed documentation.
Choose it for An agent that sends a prepared PDF or a saved template for signature from one company account and tracks it to completion by webhook or polling, with the signed PDF and audit trail at the end.
Strengths
- Public OpenAPI 3.0.3 spec with 74 operations, plus llms.txt and a Markdown copy of every docs page
- Free test mode works on every endpoint from a free account, with watermarked, non-binding requests that don't count against quota
- Error catalogue of 20 HTTP error names with cause, remediation and a retryable flag, also embedded in the spec as
x-error-codes
Weaknesses
- No idempotency keys found in the docs or the spec, so a retried send can create a second signature request
- An API key grants full access to the account, with no scoped or read-only keys. Scopes exist only on OAuth tokens
- OAuth apps need manual approval by Dropbox Sign support before production use
Price PaidAuth OAuth or keyx402 nohosted
airSlate SignNow
B 68.5/100airSlate SignNow is an e-signature service. Its REST API prepares documents from templates, sends signature invites, embeds signing in other apps and reports status through webhooks. A hosted MCP server gives AI agents 20 documented tools over the same account.
Verdict The REST API has a public OpenAPI 3.0 spec with 354 operations, Markdown docs, a free Development mode with 500 invites and a hosted MCP server with OAuth. API keys don't expire and carry full account access, no idempotency keys were found, and the MCP server's GitHub repository was archived when checked on 7 October 2026.
Choose it for An agent that sends agreements from templates, embeds signing in another product or tracks invites, and teams that want per-invite pricing with a free test mode.
Strengths
- Public OpenAPI 3.0.3 spec with 354 operations, 342 of them with examples, plus llms.txt and a Markdown copy of every docs page
- Development mode is free on the production host, with 500 requests an hour and up to 500 signature invites without a plan
- Hosted MCP server at mcp-server.signnow.com/mcp with OAuth, PKCE and dynamic client registration, and read-only and destructive hints on its tools
Weaknesses
- API keys don't expire and work for all API requests. Narrower access needs an OAuth token requested with a URL-pattern scope
- No idempotency key was found in the spec or guides, and each signature invite sent is charged
- The sn-mcp-server GitHub repository was archived when checked on 7 October 2026, while the docs still send issue reports there
Price $2 / txAuth OAuth or keyx402 nohosted and local
PandaDoc
B 63.1/100PandaDoc is a document platform for proposals, quotes, contracts and e-signatures. Its REST API and hosted MCP server create documents from templates, send them for signature, embed signing sessions and report status through webhooks.
Verdict The public OpenAPI spec lists 133 operations and reached version 8.21.0 on 2 October 2026, and the hosted MCP server, with OAuth and dynamic client registration, is open to every plan including Free. The status page records three incidents affecting document creation, sending or the API between 15 July and 6 September 2026, and writes have no idempotency keys.
Choose it for Suited to agents that prepare a proposal, quote or contract from a template, send it for signature and track it, for a team that already works in PandaDoc.
Strengths
- Public OpenAPI 3.0.3 spec with 133 operations, version 8.21.0 on 2 October 2026, plus llms.txt and a Markdown copy of each docs page
- Hosted MCP server in the official MCP registry as com.pandadoc.mcp/mcp, with OAuth, PKCE and dynamic client registration
- API and MCP access on every plan including Free, and a sandbox key that isn't charged
Weaknesses
- Three incidents hit document creation, sending or the API between 15 July and 6 September 2026, the longest about 3.5 hours
- No idempotency keys, and each document created with a production credential uses one usage credit
- Production API keys need approval from Sales, and usage credit pack prices sit on the in-app billing page
Price FreemiumAuth OAuth or keyx402 nohosted
Documenso
B 62.8/100Open-source document signing platform from Documenso, Inc., self-hosted under AGPL-3.0 or used as a hosted cloud. Its REST API creates envelopes from PDFs or templates, sends them to recipients, reports status by webhook and returns the signed file.
Verdict The v2 REST API has a public OpenAPI 3.0.3 spec of 89 operations, a free plan with API access, and envelope audit logs and signing certificates by API. API tokens carry full access to one team with no narrower scopes, and writes take no idempotency key. A high-severity advisory on 2 October 2026 exposed user names and emails.
Choose it for Teams that want an e-signature API they can also self-host, with templates, embedded signing and an audit log by API.
Strengths
- Public OpenAPI 3.0.3 spec for the v2 API with 89 operations, plus llms.txt and a 1 MB llms-full.txt
- API access on every plan, the free plan included (5 documents a month, up to 10 recipients)
- Envelope audit log and signing certificate are readable and downloadable through the API
Weaknesses
- API tokens grant full access to one team. No read-only or per-resource scopes were found in the reviewed documentation
- No idempotency keys in the spec or docs, and the docs state that cancelling an envelope is not idempotent
- Advisory GHSA-3494-9j87-fj64 (CVSS 7.5, published 2 October 2026) let an unauthenticated request read user names and emails
Price FreemiumAuth API keyx402 nohosted
Docusign
B 62.5/100Docusign is an e-signature and agreement management service. Its eSignature REST API creates envelopes from documents or templates, sends them to signers, embeds signing in an app and reports status. A hosted MCP server exposes a subset as tools.
Verdict The eSignature REST API has public Swagger and OpenAPI files on GitHub, OAuth 2.0, a free developer sandbox and Connect webhooks, and the MCP server reached general availability on 30 September 2026. Production needs a paid plan from $50 a month and a Go-Live review, and the status site lists 34 incidents since 9 July 2026.
Choose it for Teams whose company already uses Docusign and needs an agent to send envelopes from templates, embed signing and track status with a full audit trail.
Strengths
- Public Spec files under MIT on GitHub for eSignature v2.1 (213 paths, 414 operations) and ten other APIs
- Free developer account with no time limit, on a separate demo environment (demo.docusign.net, mcp-d.docusign.com)
- Rate limits published with numbers (3,000 calls an hour per account, 500 per 30 seconds in production) and returned in response headers
Weaknesses
- health.docusign.com lists 34 incidents since 9 July 2026, including a two-hour NA4 disruption on 30 July and email notification failures from 25 to 30 September
- Production access needs a paid account, an admin and a Go-Live review, and MCP integration keys need Docusign's approval since 30 September 2026
- The eSignature spec is Swagger 2.0 with no enums, no required lists and no security definitions. Valid values sit in prose
Price $50 / moAuth OAuthx402 nohosted
DocuSeal
B 62.4/100Open-source document signing platform from DocuSeal, LLC, run as a hosted cloud in US and EU regions or self-hosted under AGPL-3.0. Its REST API creates templates from PDF, DOCX or HTML, sends them for signature and reports status by webhook.
Verdict The cloud REST API has a public OpenAPI 3.1 file with 23 operations, Markdown twins of every docs page, a free sandbox with its own keys and a published price of $0.20 a completed document. No rate limit, error reference or idempotency key was found in the reviewed documentation, and each user has one API key with no scopes.
Choose it for A software company adding signing to its own product, paying per completed document, with HTML, PDF tag and DOCX variable templates and embeddable forms, and a choice of US or EU hosting or self-hosting.
Strengths
- Public OpenAPI 3.1 file with 23 operations and 11 webhook events, plus llms.txt and a Markdown twin of every page
- Free Test Mode sandbox with separate API keys, isolated from production data
- Published usage price of $0.20 a completed document, with one $20 Pro seat needed to get a production key
Weaknesses
- No rate limit, 429 guidance or idempotency key was found in the API reference or the OpenAPI file
- The OpenAPI file documents only 200 responses. Error bodies and status codes are not described
- One API key per user in
X-Auth-Token, with no scopes or read-only keys found in the reviewed documentation
Price $0.20 / txAuth API keyx402 nohosted
SignWell
C 61.9/100E-signature service from Docsketch, LLC (trading as SignWell). Its REST API creates documents and templates, sends them for signature, embeds signing in an iframe and reports status by webhook. A CLI and a local MCP server use the same API.
Verdict The REST API has a public OpenAPI 3.0.1 file with 26 operations, Markdown twins of its reference pages, published rate limits and a free test mode. Each account uses one API key with no scopes found, there are no idempotency keys, and the operation that lists documents is left out of the public reference.
Choose it for A small software team adding signing to its own product at a per-document price with no seat minimum, embedded signing, requesting and template editing, and bulk send to 500 recipients.
Strengths
- Public OpenAPI 3.0.1 file with 26 operations, every one documenting a 429 response, plus llms.txt and a Markdown twin of each reference page
- Rate limits are published per key. 100 requests in 60 seconds, 30 a minute for creating documents or templates, 20 a minute in test mode
test_mode: truecreates documents that are not billed and not legally binding, with unlimited test use on the free account
Weaknesses
- One API key in
X-Api-Key, created under Settings, API. No scopes, read-only keys or expiry were found in the reviewed documentation - No idempotency key and no Retry-After guidance in the reference. The 429 body is one
errorstring - List Documents is marked
x-internalin the vendor's SDK copy of the API description and is absent from the public file, though the CLI and MCP server call it
Price $0.85 / txAuth API keyx402 nohosted and local
Adobe Acrobat Sign
D 52.6/100Adobe Acrobat Sign is an e-signature service. Its REST API v6 creates agreements from uploaded files or library templates, sends them for signature, returns signing URLs and audit trails, and reports status through webhooks.
Verdict The REST API has OAuth 2.0 scopes that can be limited to one user, a group or the account, Retry-After on throttled calls and a free Developer Edition. Adobe calls its own SDKs obsolete, the newest dated API change is November 2025, and API plans are sold through sales with no public price.
Choose it for A company that already holds Acrobat Sign Solutions and wants an agent to send agreements, track them by webhook and fetch signed files and audit trails.
Strengths
- OAuth 2.0 scopes split read, write and send per resource, each limited to the authorising user, a group or the whole account
- Throttled calls return 429 with a
Retry-Afterheader and aretryAfterbody field, and the guide asks for exponential backoff - ETags give 304 on unchanged reads and
If-Matchon updates, so a stale write fails with 412RESOURCE_MODIFIED
Weaknesses
- Adobe's SDK page says the C#, Java and JavaScript SDKs are obsolete and out of step with REST v6
- The newest dated entry in the API release notes is November 2025, eleven months before this check
- API plans (Acrobat Sign Solutions) are sold through sales. No per-transaction price is published
Price $16.99 / seat-moAuth OAuthx402 nohosted
Head to head
- Dropbox Sign vs airSlate SignNow B 68.9 vs B 68.5
- Dropbox Sign vs PandaDoc B 68.9 vs B 63.1
- Documenso vs Dropbox Sign B 62.8 vs B 68.9
- Docusign vs Dropbox Sign B 62.5 vs B 68.9
- PandaDoc vs airSlate SignNow B 63.1 vs B 68.5
- Documenso vs airSlate SignNow B 62.8 vs B 68.5
- Docusign vs airSlate SignNow B 62.5 vs B 68.5
- Documenso vs PandaDoc B 62.8 vs B 63.1
- Docusign vs PandaDoc B 62.5 vs B 63.1
- Documenso vs Docusign B 62.8 vs B 62.5
Questions
What are the highest-rated contract, proposal and e-signature APIs for AI agents?
Dropbox Sign has the highest benchmark score of the 8 ranked contract, proposal and e-signature APIs, 68.9 (B). airSlate SignNow is second with 68.5 (B).
How many contract, proposal and e-signature APIs are agent-ready?
0 of the 8 ranked here grade BB or better, the bar for agent-ready on the Anchor benchmark.
Which contract, proposal and e-signature APIs accept x402 payments?
None of the ranked listings here accepts x402 for its main call yet.
How is this list ranked?
By the Anchor benchmark score out of 100, a weighted mean of the scored categories minus deductions for negative events, from public evidence re-checked as vendors change. Listings cannot pay for a place. The latest assessment behind this page is from 9 October 2026.
How this list is made
The order is the Anchor benchmark score, the same number as on each listing and in the top list. Each listing is graded from public evidence against the benchmark checklist, and the picks above are worked out from those grades, prices and facts. No listing pays for its place, and paid audits or listing help never change a score.
Full ranked table · 28 head-to-head comparisons · Best tools in every category