ChatGPT Actions vs Claude MCP: which is better for productivity tools?

Two competing approaches have emerged for connecting AI assistants to external tools: OpenAI's Custom GPT Actions (OpenAPI spec, X-API-Key auth) and Anthropic's Model Context Protocol (JSON-RPC, OAuth or Bearer auth). ReminderIt supports both. Here's an honest comparison.

Setup complexity

ChatGPT Actions: import an OpenAPI spec by URL, set an API key in the auth settings. Medium complexity — requires building or finding a Custom GPT first. MCP (Claude Desktop): pip install + JSON config. Low complexity once you know where the config file is. MCP (Claude.ai web): paste URL + OAuth consent click. Lowest complexity of all three.

Capability depth

OpenAPI Actions are well-suited to REST APIs with clear request/response patterns. MCP tools are more flexible — they can return streaming data, handle stateful sessions, and be composed in ways OpenAPI schemas don't express well. For ReminderIt's use case, both expose the same functionality; the difference is mainly in the developer experience of extending them.

Security model

ChatGPT Actions use API key authentication in the request header — simple and effective. Claude MCP uses OAuth 2.0 with PKCE for web connections and environment-variable API keys for Desktop — more secure for multi-user hosted deployments. For personal use, both are fine.

Which to choose

Use ChatGPT Actions if you're already in the ChatGPT ecosystem and want minimal setup. Use Claude MCP if you want the richest integration experience, especially across Claude Desktop and Claude.ai in the same account. Both get you real phone calls from ReminderIt — the choice is about workflow preference.