> For clean Markdown of any page, append .md to the page URL.
> For a complete documentation index, see https://docs.merge.dev/merge-unified/supplemental-data/llms.txt.
> For AI client integration (Claude Code, Cursor, etc.), connect to the MCP server at https://docs.merge.dev/_mcp/server.

# Supplemental data

> Build once. Connect to every API, tool, and LLM. Ship products and agents to production without owning the integration stack.

## Docs

- [Supplemental Data](https://docs.merge.dev/merge-unified/supplemental-data/overview.md): Overview of ways to access data beyond Common Models — Passthrough Requests, Remote Data, Remote Field Classes, Field Mapping, and Custom Objects.
- [Remote Data](https://docs.merge.dev/merge-unified/supplemental-data/remote-data.md): How to use the ?include_remote_data=true query parameter to get the raw third-party API response alongside the normalized Common Model data.
- [Native enum values](https://docs.merge.dev/merge-unified/supplemental-data/native-enum-values.md): How to read native enum values with show_native_enum_values and write them with the _native parameters on Merge's POST and PATCH endpoints.
- [Authenticated Passthrough Request](https://docs.merge.dev/merge-unified/supplemental-data/passthrough-request/overview.md): The /passthrough endpoint. Proxy authenticated requests to the underlying third-party API when you need data or operations not covered by Common Models.
- [Making a Passthrough Request](https://docs.merge.dev/merge-unified/supplemental-data/passthrough-request/passthrough-requests.md): How to send raw HTTP requests to a third-party integration's API through Merge, using the stored Linked Account credentials.
- [Async Passthrough](https://docs.merge.dev/merge-unified/supplemental-data/passthrough-request/async-passthrough-requests.md): How to send long-running Passthrough Requests asynchronously and poll for results, avoiding API timeouts.
- [Remote Field Classes](https://docs.merge.dev/merge-unified/supplemental-data/remote-field-classes/remote-field-classes.md): Overview of Remote Field Classes — a standardized way to read and write integration-specific fields (both standard and custom) that aren't part of Common Models.
- [Pulling Remote Field Classes](https://docs.merge.dev/merge-unified/supplemental-data/remote-field-classes/pulling-data.md): How to read Remote Field Class metadata and values. Covers discovering available remote fields and including them in GET requests.
- [Pushing Remote Field Classes](https://docs.merge.dev/merge-unified/supplemental-data/remote-field-classes/pushing-data.md): How to write values to integration-specific custom fields using Remote Field Classes in POST and PATCH requests.
- [Field Mapping](https://docs.merge.dev/merge-unified/supplemental-data/field-mapping/overview.md): How Field Mapping works — create target fields on Common Models, then map third-party custom fields to them at the integration or Linked Account level.
- [Quickstart video](https://docs.merge.dev/merge-unified/supplemental-data/field-mapping/quickstart-video.md): Video walkthrough of Field Mapping setup — creating target fields, configuring mappings, and accessing mapped data.
- [Target fields](https://docs.merge.dev/merge-unified/supplemental-data/field-mapping/target-fields.md): How to create and manage target fields — the custom fields you define on Common Models that third-party data gets mapped into.
- [Mapping across an integration](https://docs.merge.dev/merge-unified/supplemental-data/field-mapping/mapping-across-an-integration.md): How to create integration-wide Field Mappings that apply to all Linked Accounts using a given integration (e.g., all Salesforce accounts).
- [Mapping for a Linked Account](https://docs.merge.dev/merge-unified/supplemental-data/field-mapping/mapping-for-a-linked-account.md): How to create Field Mappings scoped to a single Linked Account, for cases where field names or structures differ between customers.
- [Advanced mapping](https://docs.merge.dev/merge-unified/supplemental-data/field-mapping/advanced-mapping.md): How to use JSONata expressions to transform, filter, or reformat third-party field values before they land on your target fields.
- [AI data transformations](https://docs.merge.dev/merge-unified/supplemental-data/field-mapping/ai-data-transformations.md): How to use Merge's AI assistant to auto-generate JSONata transformation expressions for Field Mapping, instead of writing them manually.
- [Access mapped data](https://docs.merge.dev/merge-unified/supplemental-data/field-mapping/access-mapped-data.md): How to read mapped field values from the API and view mapping configurations in the Merge Dashboard.
- [Custom Objects](https://docs.merge.dev/merge-unified/supplemental-data/custom-objects.md): How to read, create, and update custom objects (non-standard object types) in CRM integrations through Merge's Custom Object endpoints.