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Once an account is linked, you can call its actions from your product. For the full journey up to that point — API key, connector profile, account linking — see the Embed overview.
Actions are the atomic operations in StackOne: salesforce_list_contacts, gmail_send_message, google_drive_list_files, etc. Every protocol is just a different way to invoke the same underlying actions.
All protocols route through the same engine, so authentication, rate limiting, data transformation, and error recovery are handled for every action. The choice comes down to your use case and how you’re building.

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Protocols

Agent SDK

Native TypeScript/Python with framework integrations (LangChain, CrewAI, OpenAI)

MCP

Open standard for AI tools. Works with Claude, Cursor, Vercel AI, n8n

A2A

Call a pre-built agent per integration, for multi-agent orchestration.

RPC/HTTP

Call an action from any backend or script with no agent or framework.

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Which protocol?

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Mixing protocols

Many production setups combine protocols. They all use the same actions and authentication, so you can mix and match:
  • RPC/HTTP for backend jobs (scheduled syncs, data pipelines)
  • Agent SDK for your product (customer-facing AI features)
  • MCP for internal tools (Cursor, Claude Desktop for your team)
  • A2A for complex workflows (multi-agent orchestration)
Exposing hundreds of actions? Use Tool Discovery so the agent searches at runtime instead of overloading its context window. It works through both MCP (search_execute mode) and the SDK (tool search).