MCP Servers Need Interactive UI - Raw JSON Is Not Enough
Raw JSON Responses Are Holding MCP Back
Right now, most MCP servers work like this: the agent calls a tool, gets back a blob of JSON, and has to figure out what to do with it. For simple tools - "get the current weather" - this works fine. For complex tools like calendar management, it falls apart.
The Calendar Problem
Ask an MCP-connected agent to "find a time to meet with Sarah next week." The calendar server returns raw JSON with every event for the next seven days. The agent parses through it, identifies gaps, cross-references with Sarah's availability (another JSON blob), and proposes a time.
This works sometimes. But the agent might miss a recurring event that doesn't show up in the query. It might not understand timezone differences encoded in the JSON. It might propose a slot during your lunch break because the calendar entry was labeled ambiguously.
What Interactive UI Looks Like
Instead of returning raw data, the MCP server should return structured responses with built-in actions. Think of it like returning a mini-application instead of a data dump.
A calendar query could return: available slots rendered as a selectable list, each with a "book this" action attached. Conflicts highlighted with explanations. Timezone-aware formatting already applied. The agent presents options, the user picks one, and the action executes without the agent needing to construct another API call.
Why This Matters Beyond Calendars
The same pattern applies to email triage, project management, CRM updates, and any tool where the user needs to make a choice from structured options. Return the options with actions attached, not raw data that the agent has to reassemble into something useful.
The MCP Spec Can Support This
MCP already supports rich content types in responses. The limitation isn't the protocol - it's that server developers default to returning JSON because it's easy to implement. Building interactive responses takes more work upfront but dramatically improves reliability.
The servers that get this right will become the standard. Raw JSON returns will feel like command-line tools in a world that expects GUIs.
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Fazm is an open source macOS AI agent. Open source on GitHub.