feat: Add constants for Well-Known URIs

src/a2a/client/client.py

@@ -27,6 +27,9 @@
     SetTaskPushNotificationConfigRequest,
     SetTaskPushNotificationConfigResponse,
 )
+from a2a.utils.constants import (
+    AGENT_CARD_WELL_KNOWN_PATH,
+)
 from a2a.utils.telemetry import SpanKind, trace_class
 
 
@@ -40,8 +43,8 @@ def __init__(
         self,
         httpx_client: httpx.AsyncClient,
         base_url: str,
-        agent_card_path: str = '/.well-known/agent.json',
-    ):
+        agent_card_path: str = AGENT_CARD_WELL_KNOWN_PATH,
+    ) -> None:
         """Initializes the A2ACardResolver.
 
         Args:
@@ -184,7 +187,7 @@ async def _apply_interceptors(
     async def get_client_from_agent_card_url(
         httpx_client: httpx.AsyncClient,
         base_url: str,
-        agent_card_path: str = '/.well-known/agent.json',
+        agent_card_path: str = AGENT_CARD_WELL_KNOWN_PATH,
         http_kwargs: dict[str, Any] | None = None,
     ) -> 'A2AClient':
         """Fetches the public AgentCard and initializes an A2A client.

src/a2a/server/apps/jsonrpc/fastapi_app.py

@@ -4,18 +4,23 @@
 
 from fastapi import FastAPI, Request, Response
 
 from a2a.server.apps.jsonrpc.jsonrpc_app import (
     CallContextBuilder,
     JSONRPCApplication,
 )
 from a2a.server.request_handlers.jsonrpc_handler import RequestHandler
 from a2a.types import AgentCard
+from a2a.utils.constants import (
+    AGENT_CARD_WELL_KNOWN_PATH,
+    DEFAULT_RPC_URL,
+    EXTENDED_AGENT_CARD_PATH,
+)
 
 
 logger = logging.getLogger(__name__)
 
 
 class A2AFastAPIApplication(JSONRPCApplication):
     """A FastAPI application implementing the A2A protocol server endpoints.
 
     Handles incoming JSON-RPC requests, routes them to the appropriate
@@ -23,38 +28,38 @@
     (SSE).
     """
 
     def __init__(
         self,
         agent_card: AgentCard,
         http_handler: RequestHandler,
         extended_agent_card: AgentCard | None = None,
         context_builder: CallContextBuilder | None = None,
-    ):
+    ) -> None:
         """Initializes the A2AStarletteApplication.
 
         Args:
             agent_card: The AgentCard describing the agent's capabilities.
             http_handler: The handler instance responsible for processing A2A
               requests via http.
             extended_agent_card: An optional, distinct AgentCard to be served
               at the authenticated extended card endpoint.
             context_builder: The CallContextBuilder used to construct the
               ServerCallContext passed to the http_handler. If None, no
               ServerCallContext is passed.
         """
         super().__init__(
             agent_card=agent_card,
             http_handler=http_handler,
             extended_agent_card=extended_agent_card,
             context_builder=context_builder,
         )
 
     def add_routes_to_app(
         self,
         app: FastAPI,
-        agent_card_url: str = '/.well-known/agent.json',
-        rpc_url: str = '/',
-        extended_agent_card_url: str = '/agent/authenticatedExtendedCard',
+        agent_card_url: str = AGENT_CARD_WELL_KNOWN_PATH,
+        rpc_url: str = DEFAULT_RPC_URL,
+        extended_agent_card_url: str = EXTENDED_AGENT_CARD_PATH,
     ) -> None:
         """Adds the routes to the FastAPI application.
 
@@ -83,9 +88,9 @@
 
     def build(
         self,
-        agent_card_url: str = '/.well-known/agent.json',
-        rpc_url: str = '/',
-        extended_agent_card_url: str = '/agent/authenticatedExtendedCard',
+        agent_card_url: str = AGENT_CARD_WELL_KNOWN_PATH,
+        rpc_url: str = DEFAULT_RPC_URL,
+        extended_agent_card_url: str = EXTENDED_AGENT_CARD_PATH,
         **kwargs: Any,
     ) -> FastAPI:
         """Builds and returns the FastAPI application instance.

src/a2a/server/apps/jsonrpc/jsonrpc_app.py

@@ -42,6 +42,10 @@
     TaskResubscriptionRequest,
     UnsupportedOperationError,
 )
+from a2a.utils.constants import (
+    AGENT_CARD_WELL_KNOWN_PATH,
+    DEFAULT_RPC_URL,
+)
 from a2a.utils.errors import MethodNotImplementedError
 
 
@@ -109,7 +113,7 @@ def __init__(
         http_handler: RequestHandler,
         extended_agent_card: AgentCard | None = None,
         context_builder: CallContextBuilder | None = None,
-    ):
+    ) -> None:
         """Initializes the A2AStarletteApplication.
 
         Args:
@@ -299,24 +303,32 @@ async def _process_non_streaming_request(
                     request_obj, context
                 )
             case SetTaskPushNotificationConfigRequest():
-                handler_result = await self.handler.set_push_notification_config(
-                    request_obj,
-                    context,
+                handler_result = (
+                    await self.handler.set_push_notification_config(
+                        request_obj,
+                        context,
+                    )
                 )
             case GetTaskPushNotificationConfigRequest():
-                handler_result = await self.handler.get_push_notification_config(
-                    request_obj,
-                    context,
+                handler_result = (
+                    await self.handler.get_push_notification_config(
+                        request_obj,
+                        context,
+                    )
                 )
             case ListTaskPushNotificationConfigRequest():
-                handler_result = await self.handler.list_push_notification_config(
-                    request_obj,
-                    context,
+                handler_result = (
+                    await self.handler.list_push_notification_config(
+                        request_obj,
+                        context,
+                    )
                 )
             case DeleteTaskPushNotificationConfigRequest():
-                handler_result = await self.handler.delete_push_notification_config(
-                    request_obj,
-                    context,
+                handler_result = (
+                    await self.handler.delete_push_notification_config(
+                        request_obj,
+                        context,
+                    )
                 )
             case _:
                 logger.error(
@@ -424,8 +436,8 @@ async def _handle_get_authenticated_extended_agent_card(
     @abstractmethod
     def build(
         self,
-        agent_card_url: str = '/.well-known/agent.json',
-        rpc_url: str = '/',
+        agent_card_url: str = AGENT_CARD_WELL_KNOWN_PATH,
+        rpc_url: str = DEFAULT_RPC_URL,
         **kwargs: Any,
     ) -> FastAPI | Starlette:
         """Builds and returns the JSONRPC application instance.

src/a2a/server/apps/jsonrpc/starlette_app.py

@@ -5,18 +5,23 @@
 from starlette.applications import Starlette
 from starlette.routing import Route
 
 from a2a.server.apps.jsonrpc.jsonrpc_app import (
     CallContextBuilder,
     JSONRPCApplication,
 )
 from a2a.server.request_handlers.jsonrpc_handler import RequestHandler
 from a2a.types import AgentCard
+from a2a.utils.constants import (
+    AGENT_CARD_WELL_KNOWN_PATH,
+    DEFAULT_RPC_URL,
+    EXTENDED_AGENT_CARD_PATH,
+)
 
 
 logger = logging.getLogger(__name__)
 
 
 class A2AStarletteApplication(JSONRPCApplication):
     """A Starlette application implementing the A2A protocol server endpoints.
 
     Handles incoming JSON-RPC requests, routes them to the appropriate
@@ -24,37 +29,37 @@
     (SSE).
     """
 
     def __init__(
         self,
         agent_card: AgentCard,
         http_handler: RequestHandler,
         extended_agent_card: AgentCard | None = None,
         context_builder: CallContextBuilder | None = None,
-    ):
+    ) -> None:
         """Initializes the A2AStarletteApplication.
 
         Args:
             agent_card: The AgentCard describing the agent's capabilities.
             http_handler: The handler instance responsible for processing A2A
               requests via http.
             extended_agent_card: An optional, distinct AgentCard to be served
               at the authenticated extended card endpoint.
             context_builder: The CallContextBuilder used to construct the
               ServerCallContext passed to the http_handler. If None, no
               ServerCallContext is passed.
         """
         super().__init__(
             agent_card=agent_card,
             http_handler=http_handler,
             extended_agent_card=extended_agent_card,
             context_builder=context_builder,
         )
 
     def routes(
         self,
-        agent_card_url: str = '/.well-known/agent.json',
-        rpc_url: str = '/',
-        extended_agent_card_url: str = '/agent/authenticatedExtendedCard',
+        agent_card_url: str = AGENT_CARD_WELL_KNOWN_PATH,
+        rpc_url: str = DEFAULT_RPC_URL,
+        extended_agent_card_url: str = EXTENDED_AGENT_CARD_PATH,
     ) -> list[Route]:
         """Returns the Starlette Routes for handling A2A requests.
 
@@ -95,9 +100,9 @@
     def add_routes_to_app(
         self,
         app: Starlette,
-        agent_card_url: str = '/.well-known/agent.json',
-        rpc_url: str = '/',
-        extended_agent_card_url: str = '/agent/authenticatedExtendedCard',
+        agent_card_url: str = AGENT_CARD_WELL_KNOWN_PATH,
+        rpc_url: str = DEFAULT_RPC_URL,
+        extended_agent_card_url: str = EXTENDED_AGENT_CARD_PATH,
     ) -> None:
         """Adds the routes to the Starlette application.
 
@@ -116,9 +121,9 @@
 
     def build(
         self,
-        agent_card_url: str = '/.well-known/agent.json',
-        rpc_url: str = '/',
-        extended_agent_card_url: str = '/agent/authenticatedExtendedCard',
+        agent_card_url: str = AGENT_CARD_WELL_KNOWN_PATH,
+        rpc_url: str = DEFAULT_RPC_URL,
+        extended_agent_card_url: str = EXTENDED_AGENT_CARD_PATH,
         **kwargs: Any,
     ) -> Starlette:
         """Builds and returns the Starlette application instance.

src/a2a/utils/__init__.py

@@ -5,6 +5,11 @@
     new_data_artifact,
     new_text_artifact,
 )
+from a2a.utils.constants import (
+    AGENT_CARD_WELL_KNOWN_PATH,
+    DEFAULT_RPC_URL,
+    EXTENDED_AGENT_CARD_PATH,
+)
 from a2a.utils.helpers import (
     append_artifact_to_task,
     are_modalities_compatible,
@@ -24,6 +29,9 @@
 
 
 __all__ = [
+    'AGENT_CARD_WELL_KNOWN_PATH',
+    'DEFAULT_RPC_URL',
+    'EXTENDED_AGENT_CARD_PATH',
     'append_artifact_to_task',
     'are_modalities_compatible',
     'build_text_artifact',

src/a2a/utils/constants.py

@@ -0,0 +1,5 @@
+"""Constants for well-known URIs used throughout the A2A Python SDK."""
+
+AGENT_CARD_WELL_KNOWN_PATH = '/.well-known/agent.json'
+EXTENDED_AGENT_CARD_PATH = '/agent/authenticatedExtendedCard'
+DEFAULT_RPC_URL = '/'