Best Unified API for CRM in 2026

July 12, 2026

Most guides to the best unified API for CRM sort vendors by architecture and integration count. Both matter less than the two questions a CRM buyer actually has to answer: what can you write back, and how are the objects designed. Unified.to and Apideck are both pass-through, so caching is not the fork between them. What separates the options is write depth per CRM and whether one call returns an enriched record or a pile of parts you assemble yourself.

TL;DR: For CRM, the real fork is write depth and object design, not caching. Unified.to publishes read, write, and change-event coverage across 57 CRM integrations, of which 51 accept writes, and embeds related records in one object where competitors make you assemble them. Merge fits enterprise breadth; Nango fits open-source control.

What is the best unified API for CRM in 2026?

The best fit depends on writes and schema, not on who caches. Unified.to leads for products needing bidirectional CRM sync across 57 integrations with per-object write depth published. Merge fits enterprise teams prioritizing observability. Apideck fits embedded marketplace UI. Nango fits open-source customization. Both Unified.to and Apideck store no data at rest.

New to the category? Start with the primer on what a unified API is, then come back for the CRM-specific detail. A quick orientation before the detail. Merge uses a sync-and-store model: it polls each connected system, normalizes the data, and stores a copy in its own infrastructure, which is why its own documentation advises polling every 24 hours as a safety net. Unified.to and Apideck route each request to the source API at request time and store no customer data at rest. Nango is code-first: you own the sync logic and the OAuth app, in exchange for more engineering. The rest of this guide is about what those differences mean once you are past reading a single contact.

Why does CRM write support matter more than integration count?

Reading a contact is trivial. Creating one against five different validation models is where unified APIs diverge, and most are stronger at reads than writes. Few publish which objects accept writes per CRM. Unified.to publishes 89 writable properties across 6 objects, and 51 of its 57 CRM integrations accept writes, named rather than asserted.

Six integrations are read-only today: Bunny.com, CalendarHero, DealCloud, Marketing360, Modjo, and Rev Sport return data but do not accept writes through the unified model. Naming them is the point, so a developer planning a write path knows which six are out before they build, not after. Coverage is built from customer requests, so if you need writes on one of these, you can request it and move it up the roadmap.

How is Unified.to's CRM object model different from Merge's and Apideck's?

Unified.to embeds related CRM data inside parent objects. One Event object carries nine activity types, and Deal, Contact, and Company each hold the others' ID arrays, so one call returns an enriched record. Apideck splits the same territory across more resources, with Notes and Activities as separate objects, pushing assembly back onto you. This is unification versus merging.

Two concrete examples make the argument checkable. First, the Event object carries note, meeting, email, call, task, marketing_email, form, page_view, and its record type in a single object. On HubSpot's own API, those live behind a separate Engagements endpoint per type. Merge's CRM model shows the same split from the other side: it exposes Engagement and EngagementType as two separate objects, and Association and AssociationType as two more, so relating an interaction to its type is a join you perform rather than a field you read. Second, Unified.to's Picklist is a list-only endpoint that returns field option sets directly, which is the capability Merge packages and gates as its Field Mapping product. The schema is the argument, and it is visible in the object design rather than the marketing copy.

The inversion is worth stating plainly. Apideck's CRM API lists eleven named resources, and its own per-connector coverage tracks activities and notes as two separate objects, against Unified.to's single Event. This is not a knock on Apideck's writes, which are strong: it accepts writes on contacts across twenty of its twenty-one CRM connectors. It is a difference in object design. More first-class objects is not more capability; it is more to fetch and stitch together for the same enriched record.

As Roy Pereira, Unified.to's CEO, puts it: "Their customers make five API calls to assemble the same data you get from one of ours." That is the practical cost of merging over unification, measured in round trips.

Which CRMs does each platform actually support, and how deeply?

Coverage counts hide depth. Across the five CRMs most buyers test first, Unified.to publishes read, write, and change-event support per integration: HubSpot at 98 readable and 56 writable properties, Salesforce at 87 and 40, Pipedrive at 83 and 40, Zoho at 78 and 35, and Dynamics 365 Sales at 74 and 40 (July 2026).

How do you keep CRM data current: sync, pass-through, or webhooks?

Merge stores a synced copy and advises polling every 24 hours as a safety net. Unified.to and Apideck hit the source live on every call, so a read reflects current state. For change detection, 40 of Unified.to's 57 CRM integrations emit native events; the other 17 are covered by virtual webhooks that detect changes and deliver events (July 2026).

One limit deserves stating rather than burying. Deletion events are thin across CRM sources: only six integrations emit a contact-deleted event, five emit deal-deleted, and two emit event-deleted. Creation and update coverage is broad, but if your product depends on detecting deletions, verify that the specific CRM you need emits the event before you design around it. The 17 without native change detection include Google Contacts, Monday, Zendesk Sell, Microsoft Dynamics 365 Customer Engagement, Follow Up Boss, and Recruiterflow; for those, Unified.to's virtual webhooks poll on a managed schedule to detect changes and deliver events, so your application receives an event whether the source emits one or not.

Will your brand show on the Salesforce and HubSpot consent screen?

With Unified.to you register your own OAuth app per CRM and supply the client ID and secret, so customers see your brand on the Salesforce or HubSpot consent screen, and the credential never leaves your infrastructure. Because you hold it, you can move off Unified.to without re-authenticating every customer.

Unified.to supports 70+ OAuth 2.0 variations, with 176 integrations on the authorization-code flow and 29 on client-credentials (as of July 2026). This has two consequences buyers care about. Marketplace listings on the Salesforce AppExchange or HubSpot Marketplace generally require you to own the OAuth app, which the bring-your-own-credentials model preserves. And the unified scope model maps one permission to many source scopes: crm_company_read resolves to oauth, crm.objects.owners.read, and crm.objects.companies.read on HubSpot, so you request one scope and Unified.to translates it per integration.

Can AI agents read and write CRM data through an MCP server?

Yes. Unified.to's MCP server lets agents read and write CRM data, executed live against the source and not persisted or cached. Each MCP request is scoped to a single customer connection with no cross-tenant access, and models never see tools they are not allowed to use. Reads and writes reflect current source state.

For a CRM agent, that difference is the whole point. Merge's Agent Handler makes a fresh call to the third party for each tool call, but the normalized data it reasons over is Merge's stored copy. On Unified.to, an agent reading a Contact and its related Events, scoring the lead, and writing a Deal back to HubSpot and Salesforce works through one request path, with nothing in a sync layer between the agent and the CRM. The tool surface is filtered per connection, so an agent only ever sees the objects and actions that connection is permitted to use.

What does a CRM unified API cost at scale?

Per-linked-account pricing is cheap to start and compounds as you onboard customers; usage-based pricing does the opposite. Merge is free to 3 linked accounts, then $650/month for 10 and $65 per account beyond. Unified.to starts at $750/month for 750,000 API calls with unlimited customers, where a 100-record read counts as one call.

The crossover is arithmetic, not brand preference. Per-account pricing wins at low customer counts; usage-based pricing wins as connected customers grow, because you pay for call volume rather than for every customer who connects. Unified.to's tiers rise from Grow ($750 / 750K calls) to Pro ($1,500 / 2M calls) to Scale ($3,000 / 6M calls), with the per-call overage rate falling as volume grows. For query-heavy CRM reporting, Database Sync writes to Postgres, MySQL, MongoDB, MSSQL, CockroachDB, or MariaDB so you query your own copy instead of paying per read.

Unified.to vs. building CRM integrations natively vs. Merge

The three-way decision comes down to who owns the assembly work and how cost scales. Building natively gives total control and no vendor in the path, at the cost of maintaining every CRM connection yourself. Merge gives a mature normalized model on a sync-and-store base; for the full teardown see Merge vs Unified.to. Unified.to gives pass-through reads and writes with the matrix published.

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Frequently asked questions

Is there a unified API that supports both Salesforce and HubSpot? Yes. Unified.to covers Salesforce, HubSpot, Pipedrive, Zoho, and Microsoft Dynamics 365 Sales among 57 CRM integrations, with published per-object read and write depth for each. HubSpot has the deepest support at 98 readable and 56 writable properties; Salesforce follows at 87 readable and 40 writable (as of July 2026).

Which unified APIs support CRM writes and bidirectional sync? 51 of Unified.to's 57 CRM integrations accept writes across 6 writable objects. For bidirectional sync, pair writes with change detection: 40 of 57 emit native events, and the rest are covered by virtual webhooks. Verify deletion support specifically, since only six integrations emit a contact-deleted event today.

Merge vs Unified.to vs Apideck for CRM, which is best? Merge fits enterprise breadth and observability on a sync-and-store base. Apideck fits embedded marketplace UI, pass-through, with a more granular object model. Unified.to fits write depth and object design, pass-through, across 57 integrations with the matrix published. Unified.to and Apideck both store no customer data at rest.

What is the cheapest unified API for CRM at scale? It depends on customer count. Per-account pricing (Merge, free to 3 accounts then $650 for 10) is cheapest at low volume. Usage-based pricing (Unified.to, $750 for 750,000 calls with unlimited customers) wins as connected customers grow, since a read of up to 100 records counts as one call.

Do unified APIs support CRM custom objects and custom fields? Unified.to supports read and write on custom objects, such as Salesforce, and custom fields through unified metadata APIs, not tier-gated. Apideck exposes custom fields on lower tiers too, but gates its custom field mapping interface to the Scale plan ($1,299/month); Merge packages equivalent Field Mapping as a gated product. Unified.to returns field option sets as a standard Picklist read.

Appendix: full CRM read/write/detect matrix

Read, write, and change-event coverage for all 57 Unified.to CRM integrations, as of July 2026. Property and event counts are a snapshot and change as coverage expands; the live model pages are the current source.

Written for Unified.to by Mallory Greene.

About the author: Mallory Greene writes about generative engine optimization (GEO) and B2B content strategy through her practice, Search Everywhere. She has covered unified APIs and integration infrastructure across Unified.to's technical content library. Based in Toronto.