🚀JSON-RPC Methods in Agent-to-Agent (A2A) Protocol | Task Send, Get, Subscribe, Push Notifications

Hi all, welcome back to another

interesting video about A2A protocol.

Today we are going to see the JSON RPC

method used in the A2A

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protocol. So first let's see what is an

overview of this RPC methods. So all RPC

methods are invoked by HTTP and usually

in the post method and all the request

and response body must be in the format

of JSON RPC request or JSON RPC response

or it should be a server send event

stream. The first method we are going to

see is task send. And this method is

used to send or initiate or continue a

task from a local client to remote

client. And it's suitable for

immediately completing task or a

synchronous task or continuously polling

based for workflows uh implementation.

And this particular task send method is

using a one particular object is called

task send parameters. And this object

contains the input message and also

different parameters for the task

execution which is basically the

instruction to the remote client. And it

usually returns the current state or a

final stage of the task with the

artifacts which is the

response. And this is a sample uh JSON

schema for sending this method. The

method name is task send as you can see

here. And we pass the task ID. The task

id is generated by the client or local

agent and then whatever be the

instruction we need to send to the

remote client. The second method we are

discussing is send subscribe and it is

used for long running or streaming task

and it is only possible to send if the

agent the remote agent is supporting

this streaming capability which you can

find in the agent card

schema and it start the task. So this

method do two actions. One, it will

start the task then it will subscribe to

the updates and we can do this using a

long connection which implemented using

servers and

events and it is also using a special

object called send task streaming

response and here is a sample one. So

the name of the method and the id of the

task then the

inputs and the next schema is containing

uh the response given by each stream or

each uh stage of the streaming task

whether the state is in progress or it's

completed. when the state when

particular long-running task is

completed this state will move to

completed and then we will get the

result of that particular

response. The next method we are going

to discuss is get and this is used in to

get periodically the polling task or to

get the final task after the task is

sent after some time and it retrieves

the status artifacts and optional

history. This is also used similar to

task send. This method also use task

query

parameters and we can see the schema is

same as uh task send. So the method is

task get and the task unique identifier

and then the response will be a message

and artifact uh from the remote agent.

The history is not relevant at this

point but this is used to how long the

history needs to be maintained for this

particular task and how long the history

uh response needs to be included in the

response uh method as well. When we go

for the implementation of agent we will

uh go through this uh with the

scenarios. The next task we will be

discussing is task cancel. As the name

implies, it's used to request a

cancellation of ongoing request or task.

Um in particular scenarios maybe the

client agent decides that it it it do

not want to go for a task execution most

probably in the streaming task then it

can use this method and the response

will be the update of the task uh like

it is canled or the response is uh

successful like that and it is also use

the task query parameters and one of the

sample would be like this which will

pass in the parameter object as the task

identifier. This is usually usually a

GUID a unique identifier. For the method

purpose only we are using this just a

number. Now the next method is for the

notification push

notification and this is mainly used to

update or set the notification

configuration and it used to set the

configuration and after that then we can

the server can send the status updates

the response update to the client

objects and it streams the send task

streaming response and this also needs

to the server needs to support this

notification feature which we can find

in the agent card with a flag called

push notification is equal to true in

the capability section of the agent card

and this is the sample response task

push notification set and it will the

configuration for one particular task is

this and the endpoint is this. This

means once the server want to send some

updates, the server send the

notification to this particular URL and

from this particular uh implementation

URL, the client agent read the

notification. Now the put notification

get. So this method is used to retrieve

the configuration of the push

notification that is also used the task

ID and as it we know that the server the

agent server needs to support this

configuration which can be identified in

the agent card as push notification

equal to true and once again as sample

schema the task push notification get

and the parameters we will pass this

task identification for particular

notification.

Then task resubscribe. This is linked to

the long running or streaming task. So

we see that the long running task you

usually use server send events but it's

a connection can be disconnected. In

that scenarios the client again request

the streaming response by using the

resubscribe. then the SSC connection

will be reestablished and then the

response will be sent to uh the client

from the remote agent. So the as it we

know that it is also require the server

to support streaming and we can read

this property in the agent card and once

again the sample schema the task and

resubscribe that's the method name and

it will pass the task ID information

then the current status of the streaming

response will be sent back to the client

agent. So we have discussed uh the

important methods JSON RPC methods

today.