Due Date Calculator Skill

The tool

The API calculates current pregnancy progress, trimesters, important milestones, and time remaining until due date with week-by-week breakdowns.

Once your client is connected to the VerveKit MCP server, this appears in its tool list as DueDateCalculatorSkill. It is read-only and open-world: it fetches, it never mutates anything on your side, so most clients will call it without asking you to confirm.

{
  "name": "DueDateCalculatorSkill",
  "arguments": {
    "last_period": "2025-06-01"
  }
}

What that looks like in a conversation

You don't name the tool — the model picks it. Asking about 2025-06-01 in the terms this source covers is enough for it to reach for DueDateCalculatorSkill on its own.

Connecting

One server URL covers every skill in the catalog, including this one. Authorization is OAuth — the client opens a browser once and there is no key to paste into a config file.

{
  "mcpServers": {
    "vervekit": {
      "url": "https://api.vervekit.com/v1/mcp"
    }
  }
}

https://api.vervekit.com/v1/mcp

Per-client setup — Claude Desktop, Cursor, VS Code, ChatGPT — is on the MCP setup page.

Arguments

These are the properties on the tool's inputSchema, so a well-behaved client validates them before the call is made.

What the model gets back

The result carries a structuredContent object matching the tool's declared outputSchema, so a client can read fields without parsing prose. status is "ok" on success and error is null; a null field means the value wasn't available for that input, not that the call failed.

{
  "status": "ok",
  "error": null,
  "data": {
    "calculation_method": "last_period",
    "last_period_date": "2024-01-01",
    "estimated_conception_date": "2024-01-15",
    "due_date": "2024-10-07",
    "current_progress": {
      "days_pregnant": 715,
      "weeks_pregnant": 102,
      "days_into_week": 1,
      "formatted": "102 weeks, 1 days",
      "trimester": 3,
      "percentage_complete": 255.36
    },
    "time_until_due": {
      "days": 0,
      "weeks": 0,
      "days_extra": 0,
      "formatted": "Past due date",
      "is_overdue": true
    },
    "upcoming_milestones": [],
    "important_dates": {
      "end_first_trimester": "2024-04-01",
      "end_second_trimester": "2024-07-08",
      "full_term_begins": "2024-09-16"
    },
    "disclaimer": "This is an estimate only. Due dates can vary. Consult your healthcare provider for medical advice."
  }
}

Fields

Failure modes

Errors come back as tool errors with a sentence the model can act on, not a bare status code.

Other ways to use Due Date Calculator Skill

Set up Due Date Calculator Skill on VerveKit, or reach the same source a different way. Your VerveKit account and credits work on all of them — one key, one balance.

Frequently asked questions