Madgicx MCP and Zapier integration: Resolving the request field issue

I'm connecting a remote MCP server (Madgicx MCP, a Facebook/Meta Ads MCP server) to Zapier using MCP Client by Zapier. The connection itself works fine — I can see and select tools from the server (e.g. list_campaigns / get_campaigns_by_ad_account).

The problem is with the Request field on the trigger/action step. This field is marked required, and its placeholder is "Enter text or insert data...". According to the tool's schema, it expects a JSON object like:

json

{"account_id": "act_1228579216058928"}

However, no matter what I type into that field — whether it's a bare string or valid JSON — the underlying MCP server rejects it with a Pydantic validation error confirming Zapier sent the entire JSON text as a literal string, not as a parsed object:

1 validation error for call[get_campaigns_by_ad_account]
request
  Input should be a valid dictionary or instance of GetCampaignsByAdAccountRequest
  [type=model_type, input_value='{"account_id": "act_1228579216058928"}', input_type=str]

Note the input_type=str — this shows the Request field's raw text (including the curly braces and quotes) was passed through as-is, never converted into an actual dictionary/object before being sent as the tool's arguments.request payload.

Happy to share more details, screenshots, or the full tool schema if useful for debugging.