Business Central API Page Generator

Generates production-ready AL API page objects following Microsoft's API v2.0 standards. Handles field mappings, navigation properties, custom actions, and permission sets.

Quick Start

page [ID] "[EntityName] API"
{
    APIVersion = 'v2.0';
    APIPublisher = '[publisher]';
    APIGroup = '[group]';

    EntityCaption = '[Entity Name]';
    EntitySetCaption = '[Entity Names]';
    EntityName = '[entityName]';       // camelCase, singular
    EntitySetName = '[entityNames]';   // camelCase, plural

    PageType = API;
    SourceTable = "[Source Table]";
    DelayedInsert = true;
    ODataKeyFields = SystemId;

    AboutText = 'API endpoint for [description]. Supports GET, POST, PATCH, DELETE operations.';
    Extensible = false;
}

Endpoint URL: /api/v2.0/companies({companyId})/[entityNames]

Prerequisites

• Source table with proper primary key
• Available page ID (Object ID Ninja or manual allocation)
• Clear list of fields to expose
• Permission requirements defined

API Page Properties

Property	Guideline
APIVersion	Use 'v2.0' for modern APIs
APIPublisher	Company identifier, lowercase, no spaces
APIGroup	Logical group: sales, purchasing, inventory, finance
EntityName / EntitySetName	camelCase, singular / plural
ODataKeyFields	Prefer SystemId over business keys for stability
DelayedInsert	Always true for proper API POST behavior
AboutText	Required. Clear description of purpose and operations
Extensible	Set false to prevent breaking API contract

Layout Pattern

Fields follow this ordering in the repeater(Group):

layout
{
    area(Content)
    {
        repeater(Group)
        {
            // 1. System ID (always first, read-only)
            field(id; Rec.SystemId)
            {
                Caption = 'Id';
                Editable = false;
            }

            // 2. Business key fields (often read-only after creation)
            field(number; Rec."No.")
            {
                Caption = 'Number';
                Editable = false;
            }

            // 3. Required business fields
            field(customerNumber; Rec."Sell-to Customer No.")
            {
                Caption = 'Customer Number';
            }

            // 4. Optional business fields
            field(customerName; Rec."Sell-to Customer Name")
            {
                Caption = 'Customer Name';
                Editable = false;  // Calculated/FlowField
            }

            // 5. Calculated/summary fields (Editable = false)

            // 6. Status fields (Editable = false)

            // 7. Timestamp fields (always last)
            field(lastModifiedDateTime; Rec.SystemModifiedAt)
            {
                Caption = 'Last Modified Date Time';
                Editable = false;
            }

            // 8. Navigation properties (part/lines)
            part(salesOrderLines; "[EntityName] Lines API")
            {
                Caption = 'Lines';
                EntityName = '[entityName]Line';
                EntitySetName = '[entityName]Lines';
                SubPageLink = "Document Type" = field("Document Type"),
                              "Document No." = field("No.");
            }
        }
    }
}

Field rules:

• camelCase identifiers, clear descriptive captions
• Mark calculated/FlowFields and system fields as Editable = false
• Group related fields logically

Field Naming Conventions

AL Field	JSON Field	Pattern
"No."	number	Descriptive names
"Sell-to Customer No."	customerNumber	camelCase compound words
"Order Date"	orderDate	Remove spaces
"Amount Including VAT"	totalAmount	Simplify when clear
Status	status	Lowercase single words
SystemId	id	Standard system fields
SystemModifiedAt	lastModifiedDateTime	Descriptive timestamps

Rules: camelCase consistently, remove spaces/special characters, follow REST/JSON conventions, use standard names for common concepts (id, number, description, status).

API Design Workflow

1. Define purpose — Who consumes this API? What operations? What data? Performance requirements?
2. Plan resource model — Identify entities, relationships, navigation properties, filtering needs
3. Allocate object IDs — API pages typically in 50100-50199; keep header/lines close (e.g., 50110, 50111)
4. Implement API page(s) — Start with header, add lines page if header-lines pattern, add validation triggers and actions
5. Create permission sets — Full access and read-only variants
6. Test API — Verify CRUD operations, actions, navigation properties, error responses

Checklist

Before completing API page generation:

• API properties defined (version, publisher, group, entity names)
• AboutText property added with clear description
• Source table has proper primary key
• Fields use camelCase naming
• System fields included (id, lastModifiedDateTime)
• Calculated fields marked Editable = false
• Navigation properties defined for related tables
• Validation triggers implemented
• Custom actions added if needed
• Permission sets created
• API tested with CRUD operations

References

For complete examples, patterns, and additional guidance:

• references/api-examples.md — Full working examples (simple page, header-lines pattern), action patterns, validation triggers, HTTP test templates
• references/api-patterns.md — Common patterns (read-only, calculated fields, enums), performance considerations, security/permissions templates, tips

External Resources

• Developing a Custom API — Microsoft Docs
• OData v4.0 Protocol — API standards
• OAuth 2.0 for Business Central — Authentication