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Documentation Index

Fetch the complete documentation index at: https://docs.humandesignapi.nl/llms.txt

Use this file to discover all available pages before exploring further.

The Human Design API is designed for programmatic consumption: structured JSON, machine-readable error codes, a consistent response envelope, and a comprehensive OpenAPI spec. This makes it straightforward to integrate as a tool for AI agents and LLM workflows.

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Why This API Works Well with AI

  • Consistent structure — every response has the same envelope (success, errorCode, data)
  • Machine-readable errors — agents can branch on errorCode without parsing text
  • camelCase fields — no special casing surprises for JSON parsers
  • OpenAPI spec — import directly into tool-building frameworks
  • Deterministic — same birth data always produces the same chart

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llms.txt

This documentation site serves an auto-generated llms.txt file: 
https://docs.humandesignapi.nl/llms.txt
Feed this to your LLM for full API context. A more comprehensive llms-full.txt with the complete documentation content is also available at /llms-full.txt.

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OpenAI Function Calling

Define the API as a tool in the OpenAI function calling format: 
{
  "type": "function",
  "function": {
    "name": "generate_human_design_chart",
    "description": "Generate a Human Design personality chart from birth data. Returns type, profile, gates, channels, and centers.",
    "parameters": {
      "type": "object",
      "properties": {
        "birthdate": {
          "type": "string",
          "description": "Date of birth in YYYY-MM-DD format"
        },
        "birthtime": {
          "type": "string",
          "description": "Time of birth in HH:MM 24-hour format"
        },
        "location": {
          "type": "string",
          "description": "Birth location as city and country"
        }
      },
      "required": ["birthdate", "birthtime", "location"],
      "additionalProperties": false
    },
    "strict": true
  }
}
When the LLM invokes this tool, make the API call: 
const response = await fetch("https://api.humandesignapi.nl/v2/charts/simple", {
  method: "POST",
  headers: {
    "Content-Type": "application/json",
    "Authorization": "Bearer YOUR_API_KEY",
    "HD-Geocode-Key": "YOUR_GEOCODE_KEY",
  },
  body: JSON.stringify({ birthdate, birthtime, location }),
});

const result = await response.json();
return result.success ? result.data : { error: result.errorCode };

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Claude Tool Use

Define as an Anthropic tool: 
{
  "name": "generate_human_design_chart",
  "description": "Generate a Human Design personality chart from birth date, time, and location. Returns type, profile, gates, channels, and defined centers.",
  "input_schema": {
    "type": "object",
    "properties": {
      "birthdate": {
        "type": "string",
        "description": "Date of birth in YYYY-MM-DD format (e.g., 1990-01-15)"
      },
      "birthtime": {
        "type": "string",
        "description": "Time of birth in HH:MM 24-hour format (e.g., 14:30)"
      },
      "location": {
        "type": "string",
        "description": "Birth location as city and country (e.g., Amsterdam, The Netherlands)"
      }
    },
    "required": ["birthdate", "birthtime", "location"]
  }
}

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Coordinates Endpoint for Agents

If your agent already has latitude and longitude (e.g., from a prior geocoding step), use the coordinates endpoint to skip the geocoding key entirely: 
const response = await fetch("https://api.humandesignapi.nl/v2/charts/coordinates", {
  method: "POST",
  headers: {
    "Content-Type": "application/json",
    "Authorization": "Bearer YOUR_API_KEY",
  },
  body: JSON.stringify({
    birthdate: "1990-01-15",
    birthtime: "14:30",
    lat: 52.3676,
    lng: 4.9041,
  }),
});
This returns a full ChartResult without requiring an HD-Geocode-Key header.

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No-Code Platforms (Zapier, Make, n8n)

Use an HTTP request module with these settings:
SettingValue
MethodPOST
URLhttps://api.humandesignapi.nl/v2/charts/simple
HeadersAuthorization: Bearer YOUR_API_KEY, HD-Geocode-Key: YOUR_GEOCODE_KEY, Content-Type: application/json
Body{"birthdate": "YYYY-MM-DD", "birthtime": "HH:MM", "location": "City, Country"}
Map dynamic fields from your workflow into the body. Parse data from the response for the chart result.
Use CaseEndpointWhy
Quick personality summaryPOST /v2/charts/simpleSmaller response, all plan tiers
Full chart readingPOST /v2/chartsAll properties, advanced tier
Agent with geocodingPOST /v2/charts/coordinatesNo geocode key needed

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Error Handling for Agents

Always check success and branch on errorCode: 
if (!result.success) {
  if (result.errorCode === "CREDITS_EXHAUSTED") {
    return "Credit limit reached. Please try again later.";
  } else if (result.errorCode === "INVALID_BIRTHDATE") {
    return "Please provide the birth date in YYYY-MM-DD format.";
  } else {
    return `API error: ${result.errorCode}`;
  }
}
See the full Error Codes reference.