Module proto 

Canonical A2A protobuf message types (lf.a2a.v1) and conversions.

The message structs in this module are generated by prost from the canonical A2A v1.0 protobuf specification (proto/a2a_v1/a2a.proto, kept byte-identical to the upstream spec file), making them wire-compatible with the official Go, Python, and Java A2A SDKs.

The convert submodule provides conversions between these protobuf types and the serde domain types in the rest of this crate. Both directions are fallible with convert::ConvertError — hence TryFrom, not From, on both sides:

• TryFrom<Proto> for Domain — protobuf values can carry out-of-range enums, invalid timestamps, or missing required oneof fields.
• TryFrom<Domain> for Proto — domain values can carry data a protobuf message cannot faithfully hold: non-object metadata, a base64 Raw part that fails to decode, a count exceeding i32::MAX, or a number outside the exact-f64 range of google.protobuf.Value.

This module is pure data, like the rest of the crate: no I/O and no transport. The gRPC transports in the server and client crates generate their tonic service stubs against these message types via extern_path.

Modules

convert

Conversions between lf.a2a.v1 protobuf types and the serde domain types.

o_auth_flows

Nested message and enum types in OAuthFlows.

part

Nested message and enum types in Part.

security_scheme

Nested message and enum types in SecurityScheme.

send_message_response

Nested message and enum types in SendMessageResponse.

stream_response

Nested message and enum types in StreamResponse.

Structs

AgentCapabilities

Defines optional capabilities supported by an agent.

AgentCard

A self-describing manifest for an agent. It provides essential metadata including the agent’s identity, capabilities, skills, supported communication methods, and security requirements. Next ID: 20

AgentCardSignature

AgentCardSignature represents a JWS signature of an AgentCard. This follows the JSON format of an RFC 7515 JSON Web Signature (JWS).

AgentExtension

A declaration of a protocol extension supported by an Agent.

AgentInterface

Declares a combination of a target URL, transport and protocol version for interacting with the agent. This allows agents to expose the same functionality over multiple protocol binding mechanisms.

AgentProvider

Represents the service provider of an agent.

AgentSkill

Represents a distinct capability or function that an agent can perform.

ApiKeySecurityScheme

Defines a security scheme using an API key.

Artifact

Artifacts represent task outputs.

AuthenticationInfo

Defines authentication details, used for push notifications.

AuthorizationCodeOAuthFlow

Defines configuration details for the OAuth 2.0 Authorization Code flow.

CancelTaskRequest

Represents a request for the CancelTask method.

ClientCredentialsOAuthFlow

Defines configuration details for the OAuth 2.0 Client Credentials flow.

DeleteTaskPushNotificationConfigRequest

Represents a request for the DeleteTaskPushNotificationConfig method.

DeviceCodeOAuthFlow

Defines configuration details for the OAuth 2.0 Device Code flow (RFC 8628). This flow is designed for input-constrained devices such as IoT devices, and CLI tools where the user authenticates on a separate device.

GetExtendedAgentCardRequest

Represents a request for the GetExtendedAgentCard method.

GetTaskPushNotificationConfigRequest

Represents a request for the GetTaskPushNotificationConfig method.

GetTaskRequest

Represents a request for the GetTask method.

HttpAuthSecurityScheme

Defines a security scheme using HTTP authentication.

ImplicitOAuthFlow

Deprecated: Use Authorization Code + PKCE instead.

ListTaskPushNotificationConfigsRequest

Represents a request for the ListTaskPushNotificationConfigs method.

ListTaskPushNotificationConfigsResponse

Represents a successful response for the ListTaskPushNotificationConfigs method.

ListTasksRequest

Parameters for listing tasks with optional filtering criteria.

ListTasksResponse

Result object for ListTasks method containing an array of tasks and pagination information.

Message

Message is one unit of communication between client and server. It can be associated with a context and/or a task. For server messages, context_id must be provided, and task_id only if a task was created. For client messages, both fields are optional, with the caveat that if both are provided, they have to match (the context_id has to be the one that is set on the task). If only task_id is provided, the server will infer context_id from it.

MutualTlsSecurityScheme

Defines a security scheme using mTLS authentication.

OAuth2SecurityScheme

Defines a security scheme using OAuth 2.0.

OAuthFlows

Defines the configuration for the supported OAuth 2.0 flows.

OpenIdConnectSecurityScheme

Defines a security scheme using OpenID Connect.

Part

Part represents a container for a section of communication content. Parts can be purely textual, some sort of file (image, video, etc) or a structured data blob (i.e. JSON).

PasswordOAuthFlow

Deprecated: Use Authorization Code + PKCE or Device Code.

SecurityRequirement

Defines the security requirements for an agent.

SecurityScheme

Defines a security scheme that can be used to secure an agent’s endpoints. This is a discriminated union type based on the OpenAPI 3.2 Security Scheme Object. See: https://spec.openapis.org/oas/v3.2.0.html#security-scheme-object

SendMessageConfiguration

Configuration of a send message request.

SendMessageRequest

Represents a request for the SendMessage method.

SendMessageResponse

Represents the response for the SendMessage method.

StreamResponse

A wrapper object used in streaming operations to encapsulate different types of response data.

StringList

protolint:disable REPEATED_FIELD_NAMES_PLURALIZED A list of strings.

SubscribeToTaskRequest

Represents a request for the SubscribeToTask method.

Task

Task is the core unit of action for A2A. It has a current status and when results are created for the task they are stored in the artifact. If there are multiple turns for a task, these are stored in history.

TaskArtifactUpdateEvent

A task delta where an artifact has been generated.

TaskPushNotificationConfig

A container associating a push notification configuration with a specific task.

TaskStatus

A container for the status of a task

TaskStatusUpdateEvent

An event sent by the agent to notify the client of a change in a task’s status.

Enums

Role

Defines the sender of a message in A2A protocol communication.

TaskState

Defines the possible lifecycle states of a Task.