feat: use ProtoJSON for JSON wire payloads

Signed-off-by: Luca Muscariello <muscariello@ieee.org>

Author: muscariello

Cargo.lock

@@ -28,6 +28,8 @@ a2a-slimrpc = { package = "agntcy-a2a-slimrpc", path = "a2a-slimrpc", version =
 # Serialization
 serde = { version = "1", features = ["derive"] }
 serde_json = "1"
+pbjson = "0.7"
+pbjson-types = "0.7"
 
 # Async runtime
 tokio = { version = "1", features = ["full"] }
@@ -48,6 +50,8 @@ tonic = "0.13"
 tonic-build = "0.13"
 prost = "0.13"
 prost-types = "0.13"
+pbjson-build = "0.7"
+protoc-bin-vendored = "3"
 slim_bindings = { package = "agntcy-slim-bindings", version = "1.3.0" }
 
 # Utilities

Cargo.toml

@@ -26,7 +26,7 @@ The workspace supports:
 | `a2a` | Core A2A types, errors, events, JSON-RPC types, and wire-compatible serde behavior |
 | `a2a-client` | Async A2A client with transport abstraction and protocol negotiation from agent cards |
 | `a2a-server` | Async server framework with REST and JSON-RPC bindings built on `axum` |
-| `a2a-pb` | Protobuf schema, generated types, and native <-> protobuf conversion helpers |
+| `a2a-pb` | Protobuf schema, generated types, ProtoJSON-capable generated types, and native <-> protobuf conversion helpers |
 | `a2a-grpc` | gRPC client and server bindings built on `tonic` |
 | `a2a-slimrpc` | SLIMRPC client and server bindings built on `slim_bindings` |
 | `examples/helloworld` | Minimal runnable example agent |

README.md

@@ -13,6 +13,7 @@ name = "a2a_client"
 
 [dependencies]
 a2a = { workspace = true }
+a2a-pb = { workspace = true }
 serde = { workspace = true }
 serde_json = { workspace = true }
 tokio = { workspace = true }