Comparison
Decision rules
- Your agent runs in an MCP client (Claude, Cursor, Make, n8n) → use MCP. Richest interactive surface, and the only one with per-tool safety annotations the client can gate on automatically.
- Your agent has a shell (Claude Code, Codex, CI pipelines) → use the CLI, and add Skills so it follows proven procedure — previews, verification steps, and confirmation gates included.
- You’re building a production integration — webhooks, bulk imports, background jobs, or anything not exposed as a tool/command → use the REST API.
- You want Jason (AI SDR) programmable — approval queues, knowledge bases, offers, playbooks → MCP has the richest Jason toolset today; the REST API covers the knowledge/offer/playbook layer.
They compose
The layers are designed to be combined, not chosen once:- Skills drive an execution surface — the skill decides what to do; the CLI, MCP, or the API
does it.
reply-adapteris the pack that carries that execution layer, so it is the one to install when you want your agent operating Reply.io. - An agent can follow a skill’s procedure using MCP tools instead of CLI commands — the vendor-neutral skills describe platform operations, not surface-specific calls.
- MCP for the interactive path, REST for the exhaustive one — drop to REST for bulk imports/updates, report exports, and webhook administration that aren’t exposed as tools.
- A CLI cron job can do the weekly hygiene sweep while an MCP agent handles the conversational work in the same workspace.
Consistent everywhere
Whatever surface you choose, these hold:- One key, scoped —
domain:verbscopes (contacts:read,sequences:operate, …) behave identically on every surface. See Authentication. - One object model — contacts, lists, sequences, threads, tasks, and Jason objects carry the same IDs and semantics everywhere.
- One rate-limit budget — see Rate limits.
- Same safety expectations — see Agent safety rules.