docs: add @param and @returns TSDoc to a2a utility functions

core/src/a2a/a2a_remote_agent_utils.ts

@@ -19,7 +19,13 @@ export interface UserFunctionCall {
 }
 
 /**
- * Returns a UserFunctionCall when the event at index has a FunctionResponse.
+ * Returns a UserFunctionCall when the event at `index` contains a
+ * FunctionResponse that can be traced back to a preceding FunctionCall event.
+ *
+ * @param session - The session whose event history to inspect.
+ * @param index - Index of the candidate event to examine.
+ * @returns The matching `UserFunctionCall`, or `undefined` if the event at
+ *   `index` is not a user function-response event or has no preceding call.
  */
 export function getUserFunctionCallAt(
   session: Session,
@@ -62,6 +68,10 @@ export function getUserFunctionCallAt(
 
 /**
  * Checks if an event contains a function call with the given ID.
+ *
+ * @param event - The event to inspect.
+ * @param callId - The function call ID to look for.
+ * @returns `true` if a part in the event has a matching `functionCall.id`.
  */
 export function isFunctionCallEvent(event: AdkEvent, callId: string): boolean {
   if (!event || !event.content || !event.content.parts) {
@@ -75,6 +85,10 @@ export function isFunctionCallEvent(event: AdkEvent, callId: string): boolean {
 
 /**
  * Finds the first part with a FunctionResponse and returns the call ID.
+ *
+ * @param event - The event to inspect.
+ * @returns The `id` of the first FunctionResponse part, or `undefined` if
+ *   none is found.
  */
 export function getFunctionResponseCallId(event: AdkEvent): string | undefined {
   if (!event || !event.content || !event.content.parts) {
@@ -89,8 +103,13 @@ export function getFunctionResponseCallId(event: AdkEvent): string | undefined {
 }
 
 /**
- * Returns content parts for all events not present in the remote session
- * and a2a contextId if found in a remote agent event metadata.
+ * Returns A2A content parts for all events not yet seen by the remote agent,
+ * along with the A2A context ID found in the most recent remote agent event.
+ *
+ * @param ctx - The current invocation context, used to identify the remote
+ *   agent's authored events.
+ * @param session - The local session whose event history to diff.
+ * @returns An object with the missing `parts` and an optional `contextId`.
  */
 export function toMissingRemoteSessionParts(
   ctx: InvocationContext,
@@ -137,7 +156,13 @@ export function toMissingRemoteSessionParts(
 }
 
 /**
- * Wraps an agent event as a user message for context.
+ * Wraps an agent event as a user message so it can be sent as context to a
+ * remote agent that only accepts user-role messages.
+ *
+ * @param ctx - The current invocation context.
+ * @param agentEvent - The agent-authored event to reframe as a user message.
+ * @returns A new event with `author: 'user'` whose parts summarise the
+ *   original agent event's text, function calls, and function responses.
  */
 export function presentAsUserMessage(
   ctx: InvocationContext,

core/src/a2a/event_converter_utils.ts

@@ -43,6 +43,12 @@ import {toA2AParts, toGenAIPart, toGenAIParts} from './part_converter_utils.js';
 
 /**
  * Converts a session Event to an A2A Message.
+ *
+ * @param event - The ADK event to convert.
+ * @param appName - The name of the ADK application.
+ * @param userId - The ID of the current user.
+ * @param sessionId - The ID of the current session.
+ * @returns An A2A message with the event's parts and metadata.
  */
 export function toA2AMessage(
   event: AdkEvent,
@@ -63,7 +69,14 @@ export function toA2AMessage(
 }
 
 /**
- * Converts an A2A Event to a Session Event.
+ * Converts an A2A Event to an ADK Session Event.
+ *
+ * @param event - The A2A event to convert (message, task, artifact update, or
+ *   status update).
+ * @param invocationId - The ADK invocation ID to attach to the resulting event.
+ * @param agentName - The name of the agent to use as the event author.
+ * @returns The converted ADK event, or `undefined` if the A2A event type
+ *   produces no content.
  */
 export function toAdkEvent(
   event: A2AEvent,

core/src/a2a/metadata_converter_utils.ts

@@ -46,6 +46,9 @@ export enum AdkMetadataKeys {
 
 /**
  * Creates ADK Event metadata from an A2A Event.
+ *
+ * @param a2aEvent - The A2A event to extract metadata from.
+ * @returns A record containing the ADK task ID and context ID keys.
  */
 export function getAdkEventMetadata(
   a2aEvent: A2AEvent,
@@ -58,6 +61,12 @@ export function getAdkEventMetadata(
 
 /**
  * Creates A2A Event metadata from an ADK Event.
+ *
+ * @param adkEvent - The ADK event to extract metadata from.
+ * @param appName - The name of the ADK application.
+ * @param userId - The ID of the current user.
+ * @param sessionId - The ID of the current session.
+ * @returns A record of A2A metadata keys populated from the ADK event.
  */
 export function getA2AEventMetadata(
   adkEvent: AdkEvent,
@@ -91,6 +100,11 @@ export function getA2AEventMetadata(
 
 /**
  * Creates A2A Session metadata from ADK Event invocation metadata.
+ *
+ * @param appName - The name of the ADK application.
+ * @param userId - The ID of the current user.
+ * @param sessionId - The ID of the current session.
+ * @returns A record of A2A metadata keys for app name, user ID, and session ID.
  */
 export function getA2ASessionMetadata({
   appName,
@@ -110,6 +124,10 @@ export function getA2ASessionMetadata({
 
 /**
  * Creates A2A Event metadata from ADK Event actions.
+ *
+ * @param actions - The ADK event actions to extract escalation and transfer
+ *   metadata from.
+ * @returns A record with escalate and transfer-to-agent A2A metadata keys.
  */
 export function getA2AEventMetadataFromActions(
   actions: AdkEventActions,

core/src/a2a/part_converter_utils.ts

@@ -35,7 +35,11 @@ enum DataPartType {
 }
 
 /**
- * Converts GenAI Parts to A2A Parts.
+ * Converts an array of GenAI Parts to A2A Parts.
+ *
+ * @param parts - The GenAI parts to convert. Defaults to an empty array.
+ * @param longRunningToolIDs - IDs of function calls that are long-running.
+ * @returns An array of A2A parts.
  */
 export function toA2AParts(
   parts: GenAIPart[] = [],
@@ -45,7 +49,11 @@ export function toA2AParts(
 }
 
 /**
- * Converts a GenAI Part to an A2A Part.
+ * Converts a single GenAI Part to the appropriate A2A Part type.
+ *
+ * @param part - The GenAI part to convert.
+ * @param longRunningToolIDs - IDs of function calls that are long-running.
+ * @returns The corresponding A2A part (text, file, or data).
  */
 export function toA2APart(
   part: GenAIPart,
@@ -64,6 +72,9 @@ export function toA2APart(
 
 /**
  * Converts a GenAI Text Part to an A2A Text Part.
+ *
+ * @param part - The GenAI part containing a text field.
+ * @returns An A2A text part, with thought metadata attached if applicable.
  */
 export function toA2ATextPart(part: GenAIPart): A2APart {
   const a2aPart: A2APart = {kind: 'text', text: part.text || ''};
@@ -79,6 +90,10 @@ export function toA2ATextPart(part: GenAIPart): A2APart {
 
 /**
  * Converts a GenAI File Part to an A2A File Part.
+ *
+ * @param part - The GenAI part containing `fileData` or `inlineData`.
+ * @returns An A2A file part with URI or bytes depending on the source.
+ * @throws {Error} If the part contains neither `fileData` nor `inlineData`.
  */
 export function toA2AFilePart(part: GenAIPart): A2APart {
   const metadata: Record<string, unknown> = {};
@@ -112,7 +127,11 @@ export function toA2AFilePart(part: GenAIPart): A2APart {
 }
 
 /**
- * Converts a GenAI Data Part to an A2A Data Part.
+ * Converts a GenAI Data Part (function call/response or code) to an A2A Data Part.
+ *
+ * @param part - The GenAI part containing structured data.
+ * @param longRunningToolIDs - IDs of function calls that are long-running.
+ * @returns An A2A data part with the appropriate type metadata.
  */
 export function toA2ADataPart(
   part: GenAIPart,
@@ -172,6 +191,12 @@ export function toA2ADataPart(
   };
 }
 
+/**
+ * Converts an A2A Message to a GenAI Content object.
+ *
+ * @param a2aMessage - The A2A message to convert.
+ * @returns A GenAI user or model content object based on the message role.
+ */
 export function toGenAIContent(a2aMessage: Message): GenAIContent {
   const parts = toGenAIParts(a2aMessage.parts);
 
@@ -181,14 +206,21 @@ export function toGenAIContent(a2aMessage: Message): GenAIContent {
 }
 
 /**
- * Converts an A2A Part to a GenAI Part.
+ * Converts an array of A2A Parts to GenAI Parts.
+ *
+ * @param a2aParts - The A2A parts to convert.
+ * @returns An array of GenAI parts.
  */
 export function toGenAIParts(a2aParts: A2APart[]): GenAIPart[] {
   return a2aParts.map((a2aPart) => toGenAIPart(a2aPart));
 }
 
 /**
- * Converts an A2A Part to a GenAI Part.
+ * Converts a single A2A Part to the appropriate GenAI Part type.
+ *
+ * @param a2aPart - The A2A part to convert.
+ * @returns The corresponding GenAI part.
+ * @throws {Error} If the A2A part has an unrecognized `kind`.
  */
 export function toGenAIPart(a2aPart: A2APart): GenAIPart {
   if (a2aPart.kind === 'text') {
@@ -208,6 +240,9 @@ export function toGenAIPart(a2aPart: A2APart): GenAIPart {
 
 /**
  * Converts an A2A Text Part to a GenAI Part.
+ *
+ * @param a2aPart - The A2A text part to convert.
+ * @returns A GenAI part with `text` and optional `thought` flag.
  */
 export function toGenAIPartText(a2aPart: A2ATextPart): GenAIPart {
   return {
@@ -218,6 +253,11 @@ export function toGenAIPartText(a2aPart: A2ATextPart): GenAIPart {
 
 /**
  * Converts an A2A File Part to a GenAI Part.
+ *
+ * @param a2aPart - The A2A file part containing bytes or a URI.
+ * @returns A GenAI part with `inlineData` or `fileData` depending on the
+ *   source, with optional video metadata attached.
+ * @throws {Error} If the file part contains neither bytes nor a URI.
  */
 export function toGenAIPartFile(a2aPart: A2AFilePart): GenAIPart {
   const part: GenAIPart = {};
@@ -247,7 +287,12 @@ export function toGenAIPartFile(a2aPart: A2AFilePart): GenAIPart {
 }
 
 /**
- * Converts an A2A Data Part to a GenAI Part.
+ * Converts an A2A Data Part to the appropriate GenAI Part.
+ *
+ * @param a2aPart - The A2A data part containing structured data and type metadata.
+ * @returns A GenAI part with the appropriate function call, function response,
+ *   or code execution fields, falling back to a JSON text part if the type is
+ *   unrecognized.
  */
 export function toGenAIPartData(a2aPart: A2ADataPart): GenAIPart {
   if (!a2aPart.data) {