Copilot Studio YAML Reference

Core File Types

Trigger Types

Topics with OnRecognizedIntent have two routing mechanisms — which one matters depends on the orchestration mode:

• modelDescription — used by generative orchestration (GenerativeActionsEnabled: true). The AI orchestrator reads this to decide routing. Primary mechanism for generative agents.
• Trigger phrases (triggerQueries) — used by classic orchestration. Pattern-matched against the user's utterance. Secondary hints when generative orchestration is enabled.

System triggers (OnConversationStart, OnUnknownIntent, OnError, etc.) fire automatically and don't use either mechanism.

YAML-Only Features

These features work at runtime but are not visible in the Copilot Studio UI. Warn users that UI edits may silently remove them.

Action Types

Connector Actions (TaskDialog)

Connector actions (kind: TaskDialog) invoke external connector operations. They are stored in actions/ and require a connection reference in connectionreferences.mcs.yml.

Use /add-action to create new actions from available connectors. The schema describes the structural properties of TaskDialog and InvokeConnectorTaskAction, but the specific inputs and outputs for each connector operation are connector-specific — use the connector lookup script (connector-lookup.bundle.js) to get the full operation details.

Action Structure

Input Types

System Variables

Variable Scopes

Global variables are defined as YAML files in variables/<Name>.mcs.yml (kind: GlobalVariableComponent). aIVisibility accepts UseInAIContext (orchestrator can read and reason about the value) or Hidden (orchestrator unaware — use for flags and internal bookkeeping).

Prebuilt Entities

Power Fx Expression Reference

Only use functions from the supported list below. Copilot Studio supports a subset of Power Fx — using unsupported functions will cause errors.

# Arithmetic
value: =Text(Topic.number1 + Topic.number2)

# Date formatting
value: =Text(Now(), DateTimeFormat.UTC)

# Conditions
condition: =System.FallbackCount < 3
condition: =Topic.EndConversation = true
condition: =!IsBlank(Topic.Answer)
condition: =System.Conversation.InTestMode = true
condition: =System.SignInReason = SignInReason.SignInRequired
condition: =System.Recognizer.SelectedIntent.TopicId = "NoTopic"

# String interpolation in activity (uses {} without =)
activity: "Error: {System.Error.Message}"
activity: "Error code: {System.Error.Code}, Time (UTC): {Topic.CurrentTime}"

# Record creation
value: "={ DisplayName: Topic.NoneOfTheseDisplayName, TopicId: \"NoTopic\", TriggerId: \"NoTrigger\", Score: 1.0 }"

# Variable initialization (first assignment uses init: prefix)
variable: init:Topic.UserEmail
variable: init:Topic.CurrentTime
# Subsequent assignments omit init:
variable: Topic.UserEmail

Supported Power Fx Functions

These are all the Power Fx functions available in Copilot Studio. Do NOT use any function not on this list.

Math: Abs, Acos, Acot, Asin, Atan, Atan2, Cos, Cot, Degrees, Exp, Int, Ln, Log, Mod, Pi, Power, Radians, Rand, RandBetween, Round, RoundDown, RoundUp, Sin, Sqrt, Sum, Tan, Trunc

Text: Char, Concat, Concatenate, EncodeHTML, EncodeUrl, EndsWith, Find, Left, Len, Lower, Match, MatchAll, Mid, PlainText, Proper, Replace, Right, Search, Split, StartsWith, Substitute, Text, Trim, TrimEnds, UniChar, Upper, Value

Date/Time: Date, DateAdd, DateDiff, DateTime, DateTimeValue, DateValue, Day, EDate, EOMonth, Hour, IsToday, Minute, Month, Now, Second, Time, TimeValue, TimeZoneOffset, Today, Weekday, WeekNum, Year

Logical: And, Coalesce, If, IfError, IsBlank, IsBlankOrError, IsEmpty, IsError, IsMatch, IsNumeric, IsType, Not, Or, Switch

Table: AddColumns, Column, ColumnNames, Count, CountA, CountIf, CountRows, Distinct, DropColumns, Filter, First, FirstN, ForAll, Index, Last, LastN, LookUp, Patch, Refresh, RenameColumns, Sequence, ShowColumns, Shuffle, Sort, SortByColumns, Summarize, Table

Aggregate: Average, Max, Min, StdevP, VarP

Type conversion: AsType, Boolean, Dec2Hex, Decimal, Float, GUID, Hex2Dec, JSON, ParseJSON

Other: Blank, ColorFade, ColorValue, Error, Language, OptionSetInfo, RGBA, Trace, With

Available Templates

Templates are bundled with the plugin. Skills that use templates reference them via ${CLAUDE_SKILL_DIR}/../../templates/.