Power Platform Custom Connector Creation

Build production-ready Power Platform custom connectors and submit them to the microsoft/PowerPlatformConnectors GitHub repo. This skill covers Independent Publisher and Verified Publisher connector paths.

References: OPENAPI_EXTENSIONS.md | AUTH_PATTERNS.md | POLICY_TEMPLATES.md | CUSTOM_CODE.md | WEBHOOK_TRIGGERS.md | EXAMPLES.md | COMMON_MISTAKES.md

Quick Reference: Independent Publisher vs Verified Publisher

Decision rule: If you own the API/service, go Verified Publisher. If you're wrapping a third-party API you don't own, go Independent Publisher.

Getting Started

Required Files

Every connector directory must contain:

Directory Structure

PowerPlatformConnectors/
├── independent-publisher-connectors/
│   └── YourConnector/
│       ├── apiDefinition.swagger.json
│       ├── apiProperties.json
│       ├── readme.md
│       ├── icon.png          (optional)
│       └── script.csx        (optional)
├── certified-connectors/       (verified publishers)
├── custom-connectors/          (samples only)
├── schemas/                    (JSON Schema for validation)
│   ├── apiDefinition.swagger.schema.json
│   └── paconn-apiProperties.schema.json
└── templates/                  (starter templates)

Scaffold a New Connector

# Fork and clone the repo
git clone https://github.com/<your-fork>/PowerPlatformConnectors.git
cd PowerPlatformConnectors
git checkout dev

# Create connector directory
mkdir independent-publisher-connectors/YourConnector
cd independent-publisher-connectors/YourConnector

# Create required files (see EXAMPLES.md for complete templates)

Swagger Definition Structure (apiDefinition.swagger.json)

Critical: Must be OpenAPI 2.0 (Swagger). OpenAPI 3.0 is NOT supported.

{
  "swagger": "2.0",
  "info": {
    "version": "1.0.0",
    "title": "My Service",
    "description": "Short description (30-500 chars). No words 'API', 'Connector', or Power Platform product names.",
    "contact": {
      "name": "Your Name",
      "url": "https://github.com/yourusername",
      "email": "you@example.com"
    }
  },
  "host": "api.myservice.com",
  "basePath": "/v1",
  "schemes": ["https"],
  "consumes": ["application/json"],
  "produces": ["application/json"],
  "securityDefinitions": {},
  "security": [],
  "paths": {},
  "definitions": {},
  "x-ms-connector-metadata": [
    { "propertyName": "Website", "propertyValue": "https://myservice.com" },
    { "propertyName": "Privacy policy", "propertyValue": "https://myservice.com/privacy" },
    { "propertyName": "Categories", "propertyValue": "AI;Business Intelligence" }
  ]
}

Key rules:

• •title — Maximum 30 characters. Cannot include the words "API", "Connector", "Copilot Studio", or any Power Platform product names. Must end with an alphanumeric character (no trailing punctuation, spaces, or special chars). Must be unique and distinguishable from existing connector titles. For Independent Publishers, use the pattern: Connector Name (Independent Publisher)
• •description — Must be 30-500 characters. Cannot contain "API", "Copilot Studio", or Power Platform product names. Must be free of grammatical and spelling errors. Should concisely describe the main purpose and value of the connector
• •contact — Include name, url, and email with a valid email address
• •x-ms-connector-metadata — Required array with Website, Privacy policy, and Categories
• •schemes — Must include "https" (HTTP not allowed for production connectors)
• •host — Production host URL only. Staging, dev, and test host URLs are not allowed. Base hostname only, no path segments

File formatting:

• •Use soft tabs with 4 spaces for indentation — no hard tabs
• •Remove trailing whitespace from all lines
• •Structure the file in this order: swagger version → info → host/schemes → consumes/produces → paths → definitions → parameters

Operations (Paths)

Define actions and triggers in the paths object:

"paths": {
  "/items": {
    "get": {
      "operationId": "ListItems",
      "summary": "List all items",
      "description": "Retrieves a list of all items from the service.",
      "x-ms-visibility": "important",
      "parameters": [
        {
          "name": "status",
          "in": "query",
          "type": "string",
          "x-ms-summary": "Status",
          "description": "Filter items by their current status.",
          "x-ms-visibility": "advanced"
        }
      ],
      "responses": {
        "200": {
          "description": "Success",
          "schema": { "$ref": "#/definitions/ItemList" }
        },
        "400": {
          "description": "The request was invalid or malformed."
        },
        "404": {
          "description": "The requested resource was not found."
        }
      }
    },
    "post": {
      "operationId": "CreateItem",
      "summary": "Create an item",
      "description": "Creates a new item in the service.",
      "parameters": [
        {
          "name": "body",
          "in": "body",
          "required": true,
          "schema": { "$ref": "#/definitions/CreateItemRequest" }
        }
      ],
      "responses": {
        "201": {
          "description": "Created",
          "schema": { "$ref": "#/definitions/Item" }
        }
      }
    }
  }
}

Key rules:

• •operationId — Must be PascalCase (capitalize every word), unique across all operations. Remove all non-alpha characters — no hyphens, underscores, or spaces (e.g., get_user-info → GetUserInfo)
• •summary — Required for every operation. Must be sentence case, 80 characters or fewer, and must end with an alphanumeric character (no trailing punctuation, spaces, or special characters). Must contain only alphanumeric characters or parentheses — no slashes (/). As a naming convention: start with "List" when the operation returns multiple records, "Get" when it returns a single record. For triggers, use the format: "When a [event]" (e.g., "When a task is created")
• •summary and description must not have the same text — the description should provide additional information beyond the summary
• •description — Required for every operation and parameter. Must be a full, descriptive sentence ending in punctuation. Must not contain any URLs. Must be in English and free of grammatical or spelling errors
• •x-ms-summary — Required on every parameter and schema property. Use Title Case, matching the parameter name but without hyphens or underscores (e.g., name: "form_name" → x-ms-summary: "Form Name")
• •x-ms-visibility — Controls visibility: "important" (always shown), "advanced" (hidden under menu), "internal" (hidden from user)
• •Response schemas — Each operation should have only one response with a schema, which should be the 2XX success response (200 or 201). The default response should NOT have a schema definition — schemas belong on expected success responses only. For error responses (4xx, 5xx), provide meaningful descriptions but remove the schema property. Empty response schemas are not allowed (except when dynamic). Empty operations are not allowed — every operation must have at least one response
• •Path parameters — All path parameters (e.g., /items/{itemId}) must include "x-ms-url-encoding": "single" and must be marked "required": true
• •Reserved names — A parameter cannot be named connectionId (reserved by the platform)
• •GET operations — Cannot have body or form data parameters
• •Remove empty properties from operations and parameters unless they are explicitly required

Definitions (Schemas)

Define reusable data models in the definitions object. These are referenced via $ref in operation parameters and responses.

Key rules:

• •All objects under properties must include both a description and title property, even when nested — unless the object contains a $ref property
• •title — Must be in Title Case. Must not contain URLs
• •description — Must be a full sentence with proper punctuation. Must not contain URLs
• •Keep all other existing properties of the definition intact
• •Remove default values from objects inside properties (defaults belong on operation parameters, not schema definitions)
• •If a number or integer property's description mentions minimum or maximum values, add explicit minimum and/or maximum properties to the schema

"definitions": {
  "Task": {
    "type": "object",
    "properties": {
      "id": {
        "type": "string",
        "title": "Task ID",
        "description": "The unique identifier for the task.",
        "x-ms-summary": "Task ID"
      },
      "name": {
        "type": "string",
        "title": "Task Name",
        "description": "The display name of the task.",
        "x-ms-summary": "Task Name"
      },
      "priority": {
        "type": "integer",
        "title": "Priority",
        "description": "The priority level of the task, from 1 (highest) to 5 (lowest).",
        "x-ms-summary": "Priority",
        "minimum": 1,
        "maximum": 5
      },
      "project": {
        "$ref": "#/definitions/Project"
      }
    }
  }
}

Note: The project property uses $ref, so it does not need its own title or description.

OpenAPI Extensions Quick Reference

Copilot Studio / AI extensions:

Extended format types: date-no-tz, email, html, uri, uuid

See OPENAPI_EXTENSIONS.md for detailed examples of each extension.

Authentication Quick Reference

Configure auth in apiProperties.json under connectionParameters (or connectionParameterSets for multi-auth):

Note: Multi-auth connectors use connectionParameterSets instead of connectionParameters and are not supported in the Custom Connector Wizard — use the paconn CLI.

API Key example (apiProperties.json):

{
  "properties": {
    "connectionParameters": {
      "api_key": {
        "type": "securestring",
        "uiDefinition": {
          "constraints": { "clearText": false, "required": "true", "tabIndex": 2 },
          "description": "Your API key from the service dashboard",
          "displayName": "API Key",
          "tooltip": "Provide your API key"
        }
      }
    },
    "iconBrandColor": "#da3b01",
    "capabilities": [],
    "publisher": "Your Name",
    "stackOwner": "Service Company Name"
  }
}

Critical: Independent Publisher iconBrandColor must be "#da3b01".

See AUTH_PATTERNS.md for OAuth 2.0, AAD, and Basic Auth patterns.

Policy Templates

Policy templates transform requests/responses without custom code. Defined in apiProperties.json:

"policyTemplateInstances": [
  {
    "templateId": "setheader",
    "title": "Set Content-Type Header",
    "parameters": {
      "x-ms-apimTemplateParameter.name": "Content-Type",
      "x-ms-apimTemplateParameter.value": "application/json",
      "x-ms-apimTemplateParameter.existsAction": "override",
      "x-ms-apimTemplateParameter.newValue": "application/json"
    }
  }
]

See POLICY_TEMPLATES.md for all templates with examples.

Custom Code (script.csx)

C# code for request/response transformation when policy templates aren't sufficient.

public class Script : ScriptBase
{
    public override async Task<HttpResponseMessage> ExecuteAsync()
    {
        if (this.Context.OperationId == "MyOperation")
            return await HandleMyOperation().ConfigureAwait(false);

        // Forward all other requests unchanged
        return await this.Context.SendAsync(
            this.Context.Request, this.CancellationToken
        ).ConfigureAwait(false);
    }
}

Constraints: .NET Standard 2.0 | 2-minute timeout | 1 MB max file size | One script per connector

See CUSTOM_CODE.md for full reference with examples.

Webhook Triggers

Mark an operation as a webhook trigger with x-ms-trigger and define the notification payload:

"/hooks": {
  "x-ms-notification-content": {
    "schema": { "$ref": "#/definitions/WebhookPayload" }
  },
  "post": {
    "operationId": "WebhookTrigger",
    "summary": "When an event occurs",
    "x-ms-trigger": "single",
    "x-ms-trigger-hint": "To see it work, create a new item in the service.",
    "parameters": [
      {
        "name": "body",
        "in": "body",
        "schema": {
          "type": "object",
          "properties": {
            "callbackUrl": {
              "type": "string",
              "x-ms-notification-url": true,
              "x-ms-visibility": "internal"
            }
          }
        }
      }
    ],
    "responses": { "201": { "description": "Created" } }
  }
}

Requirements: Must also define a DELETE operation so the platform can unregister webhooks. The API must return a Location header in the 201 response pointing to the webhook resource.

See WEBHOOK_TRIGGERS.md for complete patterns.

Certification & Submission

PR Checklist

• • All files in correct directory (independent-publisher-connectors/ or certified-connectors/)
• • PR targets dev branch (never master)
• • apiDefinition.swagger.json passes swagger validation (use Solution Checker)
• • apiProperties.json matches schema
• • readme.md / intro.md follows template (Publisher, Prerequisites, Operations, Credentials, Known Issues)
• • No secrets or real API keys in any file
• • Connector title is ≤30 characters, no restricted words ("API", "Connector", "Copilot Studio")
• • Connector description is 30-500 characters
• • Host URL is a production URL (no staging/dev/test URLs)
• • Response schemas provided on success responses only (not on default response)
• • x-ms-connector-metadata array present with Website, Privacy policy, Categories
• • All summaries are ≤80 chars, end with alphanumeric, no slashes
• • All descriptions are full sentences ending in punctuation, no URLs
• • Summary and description text are not identical for any operation or parameter
• • All path parameters have required: true and x-ms-url-encoding: "single"
• • All operationId values are PascalCase with no non-alphanumeric characters
• • For OAuth connectors: "redirectMode": "GlobalPerConnector" (not "Global")
• • For Independent Publisher: iconBrandColor is "#da3b01"
• • For Independent Publisher with OAuth: detailed instructions for creating the OAuth app
• • At least 10 successful calls per operation tested
• • Screenshots of 3+ unique operations working in a Flow (Independent Publisher)
• • All strings are in English, free of spelling/grammar errors
• • JSON uses 4-space indentation, no trailing whitespace
• • Package validated with ConnectorPackageValidator.ps1

paconn CLI Deployment

# Install the CLI
pip install paconn

# Create a connector
paconn create --api-def apiDefinition.swagger.json --api-prop apiProperties.json

# With custom code and icon
paconn create --api-def apiDefinition.swagger.json --api-prop apiProperties.json \
  --script script.csx --icon icon.png

# Update an existing connector
paconn update --api-def apiDefinition.swagger.json --api-prop apiProperties.json \
  --connector-id <connector-id>

README Template

# Service Name
Short description of the service (2-3 sentences).

## Publisher: Your Name

## Prerequisites
- An account with [Service Name](https://service.com)
- An API key (obtained from Settings > API Keys)

## Supported Operations
### List Items
Retrieves all items from your account.

### Create Item
Creates a new item with the specified properties.

## Obtaining Credentials
Step-by-step instructions for getting API credentials.

## Known Issues and Limitations
- Rate limited to 100 requests per minute
- Maximum 1000 items per response

## Deployment Instructions
Run the following commands:
\`paconn create --api-def apiDefinition.swagger.json --api-prop apiProperties.json\`

Best Practices

Do:

• •Use x-ms-summary on every parameter and schema property (controls designer labels)
• •Use x-ms-visibility: "internal" for parameters with fixed values (e.g., api-version)
• •Provide default values for all internal required parameters
• •Include complete response schemas on success responses only (enables dynamic content in flows)
• •Use $ref definitions and $ref parameters for reusable schemas and shared parameters
• •Test with the custom connector wizard before submitting PR — run at least 10 successful calls per operation
• •Run Solution Checker and ConnectorPackageValidator.ps1 before submitting
• •Use policy templates before reaching for custom code
• •Use PascalCase for operationId — remove all non-alpha characters
• •Keep summary to 80 characters or fewer, sentence case, ending with an alphanumeric character
• •Ensure summaries contain only alphanumeric characters or parentheses — no slashes
• •Start summaries with "List" (returns many) or "Get" (returns one); for triggers: "When a [event]"
• •Make sure summary and description have different text on every operation/parameter
• •Write description as full sentences ending in punctuation — no URLs
• •Add title (Title Case) and description (full sentence) to all definition properties (skip for $ref)
• •Add "x-ms-url-encoding": "single" and "required": true to all path parameters
• •Add minimum/maximum when number/integer ranges are known
• •Ensure all text is in English and free of grammatical/spelling errors
• •Capitalize abbreviations to avoid translation issues
• •Use "redirectMode": "GlobalPerConnector" for all OAuth connectors
• •Use 4-space soft tabs and remove trailing whitespace in JSON files
• •Use only production host URLs (no staging, dev, or test URLs)

Don't:

• •Use OpenAPI 3.0 — must be Swagger 2.0
• •Include real API keys or secrets in files (use dummy values: <<Enter your API key>>)
• •Submit PR to master branch (always target dev)
• •Leave x-ms-connector-metadata empty or missing
• •Use wrong brand color for Independent Publisher (must be #da3b01)
• •Skip response schemas (breaks dynamic content in Power Automate)
• •Put schemas on the default response — schemas belong on explicit success responses (200/201) only
• •Exceed 1 MB for the OpenAPI definition file
• •Put schemas on error responses (4xx/5xx) — descriptions only
• •Leave default values on definition properties (only on operation parameters)
• •Include empty properties unless they are required
• •Put URLs in title or description fields
• •Name any parameter connectionId (reserved by the platform)
• •Include body or form data parameters on GET operations
• •Use "redirectMode": "Global" — must be "GlobalPerConnector" (mandatory since Feb 2024)
• •Exceed 30 characters for connector title

See COMMON_MISTAKES.md for a full error catalog with fixes.

Related Files

• •OPENAPI_EXTENSIONS.md — Detailed reference for all x-ms-* extensions with examples
• •AUTH_PATTERNS.md — API Key, OAuth 2.0 (AAD/Generic), Basic Auth, and Multi-Auth patterns
• •POLICY_TEMPLATES.md — All policy template IDs with configuration examples
• •CUSTOM_CODE.md — C# script.csx patterns, ScriptBase class, supported namespaces
• •WEBHOOK_TRIGGERS.md — Webhook trigger registration, notification, and deletion patterns
• •EXAMPLES.md — Complete working connector examples for common scenarios
• •COMMON_MISTAKES.md — Error catalog with fixes and validation tips