macalc

Calculate Pregnancy Due Date

calculate_pregnancy_due_date

Read-onlyIdempotent

Calculate due date and current gestational week from last period. Returns: {due_date}. See list_bundles for related 'sante' calculators.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "last_period_date": "<last_period_date>"
    },
    "name": "calculate_pregnancy_due_date"
  }
}

Input Schema

Name	Required	Description	Default
`last_period_date`	Yes	Last menstrual period date YYYY-MM-DD

Output Schema

Name	Required	Description
`result`	No	Computed result. Object whose fields depend on the tool (e.g. {tax, marginal_rate, brackets} for tax tools, {volume_l, gallons} for volume tools).
`source`	No	Authoritative source for the rule or formula (e.g. "Article 197 CGI", "NF DTU 21").
`formula`	No	Human-readable formula or method used (e.g. "I=P·r·t", "Magnus formula").
`reference_url`	No	Link to a calcul2 page documenting the calculation in detail.

Schema Changelog

Changes observed during successful MCP inspections.

Changed1 schema field changedApr 25, 2026

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "$schema": "http://json-schema.org/draft-07/schema#",
+  "additionalProperties": false,
+  "properties": {
+    "formula": {
+      "description": "Human-readable formula or method used (e.g. \"I=P·r·t\", \"Magnus formula\").",
+      "type": "string"
+    },
+    "reference_url": {
+      "description": "Link to a calcul2 page documenting the calculation in detail.",
+      "type": "string"
+    },
+    "result": {
+      "description": "Computed result. Object whose fields depend on the tool (e.g. {tax, marginal_rate, brackets} for tax tools, {volume_l, gallons} for volume tools)."
+    },
+    "source": {
+      "description": "Authoritative source for the rule or formula (e.g. \"Article 197 CGI\", \"NF DTU 21\").",
+      "type": "string"
+    }
+  },
+  "type": "object"
+}

First observedApr 8, 2026

TDQS

B3.2/5.0

Behavior3/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already declare the full safety profile (readOnly, idempotent, non-destructive, closed-world), so the burden is lower. The description adds that the gestational week is computed, but says nothing about behavior beyond that; a baseline 3 is appropriate given annotations carry the safety disclosure.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness4/5

Is the description appropriately sized, front-loaded, and free of redundancy?

Two short sentences, front-loaded with the core action and its input. The trailing list_bundles pointer is slightly tangential but not bloated.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness4/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a one-parameter read-only calculator with an output schema, the definition covers the essentials. The 'Returns: {due_date}' line is redundant against the output schema and slightly inconsistent with the mentioned gestational-week output, but nothing critical is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% and the single parameter is fully documented, so the schema does the heavy lifting. The description's 'from last period' aligns with last_period_date but adds no format or interpretation detail beyond it.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose4/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb+resource ('Calculate due date and current gestational week') plus the input basis ('from last period'), so the agent knows exactly what it produces. However, it does not differentiate itself from the close sibling calculate_due_date (nor calculate_ovulation/calculate_menstrual_cycle), leaving potential ambiguity.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines2/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

The only routing guidance is 'See list_bundles for related "sante" calculators,' which points at a discovery tool rather than stating when to use this calculator versus calculate_due_date or the other pregnancy/cycle siblings. No when-to-use or exclusion criteria are given.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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