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>
> Documentation indexes by section:
> - APIs and SDKs: https://docusign.docs.buildwithfern.com/docs/llms.txt
> - Platform 101: https://docusign.docs.buildwithfern.com/platform/llms.txt
> - Extension Apps: https://docusign.docs.buildwithfern.com/extension-apps/llms.txt
> - Docusign CLI: https://docusign.docs.buildwithfern.com/docusign-cli/llms.txt
>
> Authentication (OAuth, JWT Grant, M2M): https://docusign.docs.buildwithfern.com/platform/auth
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>
> OpenAPI specifications: https://docusign.docs.buildwithfern.com/openapi.json
> MCP server: https://docusign.docs.buildwithfern.com/_mcp/server

# Extension contracts

> Reference for Docusign extension contracts.

Each extension has an extension contract: a set of [actions](/extension-apps/extension-apps-101/concepts/actions) and [capabilities](/extension-apps/extension-apps-101/concepts/capabilities) that are supported for the extension.

See the contract details for each extension:

#### Connected fields

* [Connected fields](/extension-apps/extension-app-reference/extension-contracts/connected-fields)

#### Data IO

* [Data IO](/extension-apps/extension-app-reference/extension-contracts/data-io)

#### Data verification

* [Bank account owner verification](/extension-apps/extension-app-reference/extension-contracts/bank-account-owner-verification)
* [Bank account verification](/extension-apps/extension-app-reference/extension-contracts/bank-account-verification)
* [Business FEIN verification](/extension-apps/extension-app-reference/extension-contracts/business-fein-verification)
* [Email address verification](/extension-apps/extension-app-reference/extension-contracts/email-address-verification)
* [Phone verification](/extension-apps/extension-app-reference/extension-contracts/phone-verification)
* [Postal address verification](/extension-apps/extension-app-reference/extension-contracts/postal-address-verification)
* [SSN verification](/extension-apps/extension-app-reference/extension-contracts/ssn-verification)

#### File IO

* [File input cloud storage](/extension-apps/extension-app-reference/extension-contracts/file-input-cloud-storage)
* [File input system of record](/extension-apps/extension-app-reference/extension-contracts/file-input-system-of-record)
* [File output cloud storage](/extension-apps/extension-app-reference/extension-contracts/file-output-cloud-storage)
* [File output system of record](/extension-apps/extension-app-reference/extension-contracts/file-output-system-of-record)
* [File output tabular format](/extension-apps/extension-app-reference/extension-contracts/file-output-tabular-format)

To suggest an extension, please visit the [Docusign Developer Community](https://community.docusign.com/developer-59).

## Next steps

* Learn more about

  [extensions and extension points](/extension-apps/extension-apps-101/concepts/extensions-and-extension-points)

  .
* Learn

  [how extensions relate to other manifest components](/extension-apps/extension-apps-101/inside-an-extension-app)

  .

> Reference for Docusign extension contracts.

## Docs

- [Connected fields extension contract reference](https://developers.docusign.com/extension-apps/extension-app-reference/extension-contracts/connected-fields.md): Get the details for connected fields actions, the request formats, and the response formats.
- [Data IO extension contract reference](https://developers.docusign.com/extension-apps/extension-app-reference/extension-contracts/data-io.md): Learn how to implement the Docusign data IO extension.
- [Custom query language reference](https://developers.docusign.com/extension-apps/extension-app-reference/extension-contracts/custom-query-language.md): Learn about Docusign's custom query language for the data I/O extension.
- [Bank account owner verification extension contract reference](https://developers.docusign.com/extension-apps/extension-app-reference/extension-contracts/bank-account-owner-verification.md): Reference information for the bank account owner verification extension.
- [Bank account verification extension contract reference](https://developers.docusign.com/extension-apps/extension-app-reference/extension-contracts/bank-account-verification.md): Learn about the requirements to implement the bank account verification extension.
- [Business FEIN verification extension contract reference](https://developers.docusign.com/extension-apps/extension-app-reference/extension-contracts/business-fein-verification.md): Learn how to use the business FEIN verification extension.
- [Email address verification extension contract reference](https://developers.docusign.com/extension-apps/extension-app-reference/extension-contracts/email-address-verification.md): Learn how to implement the email address verification extension.
- [Phone verification extension contract reference](https://developers.docusign.com/extension-apps/extension-app-reference/extension-contracts/phone-verification.md): Learn how to use the phone verification extension.
- [Postal address verification extension contract reference](https://developers.docusign.com/extension-apps/extension-app-reference/extension-contracts/postal-address-verification.md): Learn about the requirements to implement the postal address verification extension.
- [SSN verification extension contract reference](https://developers.docusign.com/extension-apps/extension-app-reference/extension-contracts/ssn-verification.md): Learn how to use the SSN verification extension.
- [File input cloud storage extension contract reference](https://developers.docusign.com/extension-apps/extension-app-reference/extension-contracts/file-input-cloud-storage.md): Get technical details about file input cloud storage extension requests and responses.
- [File input system of record extension contract reference (beta)](https://developers.docusign.com/extension-apps/extension-app-reference/extension-contracts/file-input-system-of-record.md)
- [File output cloud storage extension contract reference](https://developers.docusign.com/extension-apps/extension-app-reference/extension-contracts/file-output-cloud-storage.md): Get technical details about file output cloud storage extension requests and responses.
- [File output system of record extension contract reference (beta)](https://developers.docusign.com/extension-apps/extension-app-reference/extension-contracts/file-output-system-of-record.md): Get technical details about file output system of record extension requests and responses.
- [File output tabular format extension contract reference](https://developers.docusign.com/extension-apps/extension-app-reference/extension-contracts/file-output-tabular-format.md): Get technical details about file output tabular format extension requests and responses.