fix(spec): Add Transport enum to specification by holtskinner · Pull Request #909 · a2aproject/A2A

holtskinner · 2025-07-24T18:55:13Z

Adds Enum of supported Transports to Specification, with extensibility for proprietary protocols.
Adds URL formatting requirement for AgentInterface.url and AgentCard.url

Co-authored-by: Stefano Maestri stefano.maestri@javalinux.it

Co-authored-by: Stefano Maestri <stefano.maestri@javalinux.it>

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Summary of Changes

Hello @holtskinner, I'm Gemini Code Assist¹! I'm currently reviewing this pull request and will post my feedback shortly. In the meantime, here's a summary to help you and other reviewers quickly get up to speed!

This pull request enhances the A2A specification by formalizing the definition of supported transport protocols. It introduces a dedicated enum for transports and significantly improves the documentation and validation of transport-related fields within the AgentCard and AgentInterface schemas. This change aims to provide clearer guidance for agents and clients on how to communicate and negotiate transport methods.

Highlights

New TransportProtocol Enum: Introduced a new TransportProtocol enum in types/src/types.ts and its corresponding definition in specification/json/a2a.json. This enum formalizes supported communication methods like JSONRPC, GRPC, and HTTP+JSON, improving clarity and standardization.
Enhanced AgentInterface Definition: The AgentInterface's transport field now leverages the new TransportProtocol enum (while retaining string extensibility). Its description has been improved, and url and transport fields now include examples and format annotations for better schema validation and documentation.
Improved AgentCard Properties: The AgentCard's preferredTransport and url properties have been updated with more detailed descriptions, examples, and default values. The additionalInterfaces property's description has been significantly expanded to include best practices for declaring multiple transport options, aiding clients in transport negotiation and fallback scenarios.

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Code Review

This pull request introduces a TransportProtocol enum to both the TypeScript types and the JSON schema to standardize supported transport protocols. By referencing the TransportProtocol enum, the schema can be more robust.

gemini-code-assist · 2025-07-24T18:56:39Z

                "preferredTransport": {
-                    "description": "The transport protocol for the preferred endpoint. Defaults to 'JSONRPC' if not specified.",
+                    "default": "JSONRPC",
+                    "description": "The transport protocol for the preferred endpoint (the main 'url' field).\nIf not specified, defaults to 'JSONRPC'.\n\nIMPORTANT: The transport specified here MUST be available at the main 'url'.\nThis creates a binding between the main URL and its supported transport protocol.\nClients should prefer this transport and URL combination when both are supported.",
+                    "examples": [
+                        "JSONRPC",
+                        "GRPC",
+                        "HTTP+JSON"
+                    ],
                    "type": "string"
                },


To ensure consistency and leverage the new TransportProtocol enum for validation, the $ref should be used to reference the enum, instead of defining default, description, and examples inline.

"description": "The transport protocol for the preferred endpoint (the main 'url' field).\nIf not specified, defaults to 'JSONRPC'.\n\nIMPORTANT: The transport specified here MUST be available at the main 'url'.\nThis creates a binding between the main URL and its supported transport protocol.\nClients should prefer this transport and URL combination when both are supported.", "$ref": "#/definitions/TransportProtocol"

gemini-code-assist · 2025-07-24T18:56:39Z

                "transport": {
-                    "description": "The transport protocol supported at this URL. This is a string to allow for future\nextension. Core supported transports include 'JSONRPC', 'GRPC', and 'HTTP+JSON'.",
+                    "description": "The transport protocol supported at this URL.",
+                    "examples": [
+                        "JSONRPC",
+                        "GRPC",
+                        "HTTP+JSON"
+                    ],
                    "type": "string"
                },


To leverage the newly added TransportProtocol enum for validation, the $ref should be used to reference the enum, instead of defining description and examples inline.

"description": "The transport protocol supported at this URL.", "$ref": "#/definitions/TransportProtocol"

🤖 I have created a release *beep* *boop* --- ## [0.3.0](v0.2.6...v0.3.0) (2025-07-30) ### ⚠ BREAKING CHANGES * Add mTLS to SecuritySchemes, add oauth2 metadata url field, allow Skills to specify Security ([#901](#901)) * Change Well-Known URI for Agent Card hosting from `agent.json` to `agent-card.json` ([#841](#841)) * Add method for fetching extended card ([#929](#929)) ### Features * Add `signatures` to the `AgentCard` ([#917](#917)) ([ef4a305](ef4a305)) * Add method for fetching extended card ([#929](#929)) ([2cd7d98](2cd7d98)) * Add mTLS to SecuritySchemes, add oauth2 metadata url field, allow Skills to specify Security ([#901](#901)) ([e162c0c](e162c0c)) ### Bug Fixes * **spec:** Add `SendMessageRequest.request` `json_name` mapping to `message` ([#904](#904)) ([2eef3f6](2eef3f6)) * **spec:** Add Transport enum to specification ([#909](#909)) ([e834347](e834347)) ### Code Refactoring * Change Well-Known URI for Agent Card hosting from `agent.json` to `agent-card.json` ([#841](#841)) ([0858ddb](0858ddb)) --- This PR was generated with [Release Please](https://github.com/googleapis/release-please). See [documentation](https://github.com/googleapis/release-please#release-please). Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>

🤖 I have created a release *beep* *boop* --- ## [0.3.0](v0.2.16...v0.3.0) (2025-07-31) ### ⚠ BREAKING CHANGES * **deps:** Make opentelemetry an optional dependency ([#369](#369)) * **spec:** Update Agent Card Well-Known Path to `/.well-known/agent-card.json` ([#320](#320)) * Remove custom `__getattr__` and `__setattr__` for `camelCase` fields in `types.py` ([#335](#335)) * Add mTLS to SecuritySchemes, add oauth2 metadata url field, allow Skills to specify Security ([#362](#362)) * Support for serving agent card at deprecated path ([#352](#352)) ### Features * Add `metadata` as parameter to `TaskUpdater.update_status()` ([#371](#371)) ([9444ed6](9444ed6)) * Add mTLS to SecuritySchemes, add oauth2 metadata url field, allow Skills to specify Security ([#362](#362)) ([be6c517](be6c517)) * Add RESTful API Serving ([#348](#348)) ([82a6b7c](82a6b7c)) * Add server-side support for plumbing requested and activated extensions ([#333](#333)) ([4d5b92c](4d5b92c)) * Allow agent cards (default and extended) to be dynamic ([#365](#365)) ([ee92aab](ee92aab)) * Support for serving agent card at deprecated path ([#352](#352)) ([2444034](2444034)) * support non-blocking `sendMessage` ([#349](#349)) ([70b4999](70b4999)) * Type update to support fetching extended card ([#361](#361)) ([83304bb](83304bb)) ### Bug Fixes * Add Input Validation for Task Context IDs in new_task Function ([#340](#340)) ([a7ed7ef](a7ed7ef)) * **deps:** Reduce FastAPI library required version to `0.95.0` ([#372](#372)) ([a319334](a319334)) * Remove `DeprecationWarning` for regular properties ([#345](#345)) ([2806f3e](2806f3e)) * **spec:** Add `SendMessageRequest.request` `json_name` mapping to `message` proto ([bc97cba](bc97cba)) * **spec:** Add Transport enum to specification (a2aproject/A2A#909) ([d9e463c](d9e463c)) ### Documentation * Address typos in docstrings and docs. ([#370](#370)) ([ee48d68](ee48d68)) ### Miscellaneous Chores * Add support for authenticated extended card method ([#356](#356)) ([b567e80](b567e80)) ### Code Refactoring * **deps:** Make opentelemetry an optional dependency ([#369](#369)) ([9ad8b96](9ad8b96)) * Remove custom `__getattr__` and `__setattr__` for `camelCase` fields in `types.py` ([#335](#335)) ([cd94167](cd94167)) * **spec:** Update Agent Card Well-Known Path to `/.well-known/agent-card.json` ([#320](#320)) ([270ea9b](270ea9b)) --- This PR was generated with [Release Please](https://github.com/googleapis/release-please). See [documentation](https://github.com/googleapis/release-please#release-please). Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>

🤖 I have created a release *beep* *boop* --- ## [0.3.0](a2aproject/A2A@v0.2.6...v0.3.0) (2025-07-30) ### ⚠ BREAKING CHANGES * Add mTLS to SecuritySchemes, add oauth2 metadata url field, allow Skills to specify Security ([#901](a2aproject/A2A#901)) * Change Well-Known URI for Agent Card hosting from `agent.json` to `agent-card.json` ([#841](a2aproject/A2A#841)) * Add method for fetching extended card ([#929](a2aproject/A2A#929)) ### Features * Add `signatures` to the `AgentCard` ([#917](a2aproject/A2A#917)) ([e799342](a2aproject/A2A@e799342)) * Add method for fetching extended card ([#929](a2aproject/A2A#929)) ([ae89f89](a2aproject/A2A@ae89f89)) * Add mTLS to SecuritySchemes, add oauth2 metadata url field, allow Skills to specify Security ([#901](a2aproject/A2A#901)) ([a5c881e](a2aproject/A2A@a5c881e)) ### Bug Fixes * **spec:** Add `SendMessageRequest.request` `json_name` mapping to `message` ([#904](a2aproject/A2A#904)) ([273a1f1](a2aproject/A2A@273a1f1)) * **spec:** Add Transport enum to specification ([#909](a2aproject/A2A#909)) ([3076ae6](a2aproject/A2A@3076ae6)) ### Code Refactoring * Change Well-Known URI for Agent Card hosting from `agent.json` to `agent-card.json` ([#841](a2aproject/A2A#841)) ([c20c28b](a2aproject/A2A@c20c28b)) --- This PR was generated with [Release Please](https://github.com/googleapis/release-please). See [documentation](https://github.com/googleapis/release-please#release-please). Co-authored-by: release-please[bot] <55107282+release-please[bot]@users.noreply.github.com>

fix(spec): Add Transport enum to specification

747dda0

Co-authored-by: Stefano Maestri <stefano.maestri@javalinux.it>

holtskinner requested a review from a team as a code owner July 24, 2025 18:55

Merge branch 'main' into add-transport

5fc8fda

gemini-code-assist Bot reviewed Jul 24, 2025

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holtskinner merged commit e834347 into main Jul 24, 2025
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gemini-code-assist Bot reviewed Jul 24, 2025

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holtskinner deleted the add-transport branch July 24, 2025 18:56

release-please Bot mentioned this pull request Jul 24, 2025

chore(main): release 0.3.0 #906

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This was referenced Jul 24, 2025

docs(specification): Restructure Section 3 to clarify multi-transport #896

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feat(spec): Update A2A types from specification 🤖 a2aproject/a2a-python#347

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release-please Bot mentioned this pull request Jul 29, 2025

chore(main): release 0.3.0 a2aproject/a2a-python#337

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a2a-bot mentioned this pull request Nov 19, 2025

chore(main): release 0.3.15 a2aproject/a2a-python#555

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ishymko mentioned this pull request Mar 11, 2026

chore(1.0-dev): release 1.0.0-alpha.0 ishymko/a2a-python#1

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a2a-bot mentioned this pull request Mar 12, 2026

chore(1.0-dev): release 1.0.0-alpha.0 a2aproject/a2a-python#818

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fix(spec): Add Transport enum to specification#909

fix(spec): Add Transport enum to specification#909
holtskinner merged 2 commits into
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add-transport

holtskinner commented Jul 24, 2025 •

edited

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holtskinner commented Jul 24, 2025 •

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