feat(spec)!: support arrays and primitives in DataPart

[matoushavlena]

Changes DataPart.data from google.protobuf.Struct to google.protobuf.Value to support JSON arrays, primitives, and other non-object values.

Breaking change: The protobuf field type changes from Struct to Value. Code that directly accesses DataPart.data as a struct/map will need to be updated to handle the broader Value type, which can be an object, array, string, number, boolean, or null.

Resolves #1088
Related #1255

[gemini-code-assist]

Summary of Changes

Hello @matoushavlena, 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 significantly enhances the flexibility of the DataPart protobuf message by changing its underlying data type from a Struct to a Value. This allows DataPart to accommodate a full spectrum of JSON types, including arrays and primitive values, rather than being limited to only structured objects. While this introduces a breaking change, it broadens the utility of DataPart for various machine-readable information exchanges, with all documentation updated accordingly.

Highlights

• Expanded DataPart Support: The DataPart.data field now utilizes google.protobuf.Value instead of google.protobuf.Struct, enabling it to encapsulate any JSON value, including objects, arrays, strings, numbers, booleans, or null.
• Breaking Change: This modification constitutes a breaking change, necessitating updates to existing code that directly accesses DataPart.data while expecting a Struct (map-like) type.
• Documentation Updates: All pertinent documentation files (docs/llms.txt, docs/topics/key-concepts.md, docs/tutorials/python/8-next-steps.md, specification/grpc/a2a.proto) have been updated to accurately reflect the enhanced capabilities of DataPart.

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[gemini-code-assist]

Code Review

This pull request introduces a significant and breaking change by updating DataPart.data from google.protobuf.Struct to google.protobuf.Value. This enhancement allows DataPart to carry not just JSON objects, but any valid JSON value, including arrays and primitives. The changes are correctly implemented in the protobuf specification, and the accompanying documentation updates in llms.txt, key-concepts.md, and a2a.proto clearly reflect this new capability. I have one minor suggestion to improve the consistency of the documentation update in one of the tutorial files.

[geneknit]

/vote

[git-vote]

Vote created

@geneknit has called for a vote on feat(spec)!: support arrays and primitives in DataPart (#1306).

The members of the following teams have binding votes:

Team
@a2aproject/a2a-tsc

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[git-vote]

Vote status

So far 12.50% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
1	0	0	7

Binding votes (1)

User	Vote	Timestamp
muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00
@darrelmiller	Pending
@lerhaupt	Pending
@geneknit	Pending
@hughesthe1st	Pending
@ToddSegal	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

Non-binding votes (1)

User	Vote	Timestamp
holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[git-vote]

Vote status

So far 12.50% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
1	0	0	7

Binding votes (1)

User	Vote	Timestamp
muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00
@darrelmiller	Pending
@lerhaupt	Pending
@geneknit	Pending
@hughesthe1st	Pending
@ToddSegal	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

Non-binding votes (1)

User	Vote	Timestamp
holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[git-vote]

Vote status

So far 12.50% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
1	0	0	7

Binding votes (1)

User	Vote	Timestamp
muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00
@darrelmiller	Pending
@lerhaupt	Pending
@geneknit	Pending
@hughesthe1st	Pending
@ToddSegal	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

Non-binding votes (1)

User	Vote	Timestamp
holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[git-vote]

Vote status

So far 12.50% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
1	0	0	7

Binding votes (1)

User	Vote	Timestamp
muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00
@darrelmiller	Pending
@lerhaupt	Pending
@geneknit	Pending
@hughesthe1st	Pending
@ToddSegal	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

Non-binding votes (1)

User	Vote	Timestamp
holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[git-vote]

Vote status

So far 12.50% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
1	0	0	7

Binding votes (1)

User	Vote	Timestamp
muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00
@darrelmiller	Pending
@lerhaupt	Pending
@geneknit	Pending
@hughesthe1st	Pending
@ToddSegal	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

Non-binding votes (1)

User	Vote	Timestamp
holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[amye]

/check-vote

[git-vote]

Votes can only be checked once a day.

[git-vote]

Vote status

So far 37.50% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
3	0	0	5

Binding votes (3)

User	Vote	Timestamp
darrelmiller	In favor	2025-12-16 17:06:55.0 +00:00:00
geneknit	In favor	2025-12-16 23:41:17.0 +00:00:00
muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00
@lerhaupt	Pending
@hughesthe1st	Pending
@ToddSegal	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

Non-binding votes (1)

User	Vote	Timestamp
holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[git-vote]

Vote status

So far 37.50% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
3	0	0	5

Binding votes (3)

User	Vote	Timestamp
darrelmiller	In favor	2025-12-16 17:06:55.0 +00:00:00
geneknit	In favor	2025-12-16 23:41:17.0 +00:00:00
muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00
@lerhaupt	Pending
@hughesthe1st	Pending
@ToddSegal	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

Non-binding votes (1)

User	Vote	Timestamp
holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[git-vote]

Vote status

So far 37.50% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
3	0	0	5

Binding votes (3)

User	Vote	Timestamp
darrelmiller	In favor	2025-12-16 17:06:55.0 +00:00:00
geneknit	In favor	2025-12-16 23:41:17.0 +00:00:00
muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00
@lerhaupt	Pending
@hughesthe1st	Pending
@ToddSegal	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

Non-binding votes (1)

User	Vote	Timestamp
holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[git-vote]

Vote status

So far 50.00% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
4	0	0	4

Binding votes (4)

User	Vote	Timestamp
ToddSegal	In favor	2025-12-19 19:24:46.0 +00:00:00
darrelmiller	In favor	2025-12-16 17:06:55.0 +00:00:00
geneknit	In favor	2025-12-16 23:41:17.0 +00:00:00
muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00
@lerhaupt	Pending
@hughesthe1st	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

Non-binding votes (1)

User	Vote	Timestamp
holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[git-vote]

Vote status

So far 50.00% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
4	0	0	4

Binding votes (4)

User	Vote	Timestamp
ToddSegal	In favor	2025-12-19 19:24:46.0 +00:00:00
darrelmiller	In favor	2025-12-16 17:06:55.0 +00:00:00
geneknit	In favor	2025-12-16 23:41:17.0 +00:00:00
muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00
@lerhaupt	Pending
@hughesthe1st	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

Non-binding votes (1)

User	Vote	Timestamp
holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[git-vote]

Vote status

So far 50.00% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
4	0	0	4

Binding votes (4)

User	Vote	Timestamp
ToddSegal	In favor	2025-12-19 19:24:46.0 +00:00:00
darrelmiller	In favor	2025-12-16 17:06:55.0 +00:00:00
geneknit	In favor	2025-12-16 23:41:17.0 +00:00:00
muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00
@lerhaupt	Pending
@hughesthe1st	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

Non-binding votes (1)

User	Vote	Timestamp
holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[git-vote]

Vote status

So far 50.00% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
4	0	0	4

Binding votes (4)

User	Vote	Timestamp
ToddSegal	In favor	2025-12-19 19:24:46.0 +00:00:00
darrelmiller	In favor	2025-12-16 17:06:55.0 +00:00:00
geneknit	In favor	2025-12-16 23:41:17.0 +00:00:00
muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00
@lerhaupt	Pending
@hughesthe1st	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

Non-binding votes (1)

User	Vote	Timestamp
holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[git-vote]

Vote status

So far 50.00% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
4	0	0	4

Binding votes (4)

User	Vote	Timestamp
ToddSegal	In favor	2025-12-19 19:24:46.0 +00:00:00
darrelmiller	In favor	2025-12-16 17:06:55.0 +00:00:00
geneknit	In favor	2025-12-16 23:41:17.0 +00:00:00
muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00
@lerhaupt	Pending
@hughesthe1st	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

Non-binding votes (1)

User	Vote	Timestamp
holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[git-vote]

Vote status

So far 50.00% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
4	0	0	4

Binding votes (4)

User	Vote	Timestamp
ToddSegal	In favor	2025-12-19 19:24:46.0 +00:00:00
darrelmiller	In favor	2025-12-16 17:06:55.0 +00:00:00
geneknit	In favor	2025-12-16 23:41:17.0 +00:00:00
muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00
@lerhaupt	Pending
@hughesthe1st	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

Non-binding votes (1)

User	Vote	Timestamp
holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[git-vote]

Vote status

So far 50.00% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
4	0	0	4

Binding votes (4)

User	Vote	Timestamp
ToddSegal	In favor	2025-12-19 19:24:46.0 +00:00:00
darrelmiller	In favor	2025-12-16 17:06:55.0 +00:00:00
geneknit	In favor	2025-12-16 23:41:17.0 +00:00:00
muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00
@lerhaupt	Pending
@hughesthe1st	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

Non-binding votes (1)

User	Vote	Timestamp
holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[git-vote]

Vote status

So far 50.00% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
4	0	0	4

Binding votes (4)

User	Vote	Timestamp
ToddSegal	In favor	2025-12-19 19:24:46.0 +00:00:00
darrelmiller	In favor	2025-12-16 17:06:55.0 +00:00:00
geneknit	In favor	2025-12-16 23:41:17.0 +00:00:00
muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00
@lerhaupt	Pending
@hughesthe1st	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

Non-binding votes (1)

User	Vote	Timestamp
holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[git-vote]

Vote status

So far 50.00% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
4	0	0	4

Binding votes (4)

User	Vote	Timestamp
ToddSegal	In favor	2025-12-19 19:24:46.0 +00:00:00
darrelmiller	In favor	2025-12-16 17:06:55.0 +00:00:00
geneknit	In favor	2025-12-16 23:41:17.0 +00:00:00
muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00
@lerhaupt	Pending
@hughesthe1st	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

Non-binding votes (1)

User	Vote	Timestamp
holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[git-vote]

Vote status

So far 50.00% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
4	0	0	4

Binding votes (4)

User	Vote	Timestamp
ToddSegal	In favor	2025-12-19 19:24:46.0 +00:00:00
darrelmiller	In favor	2025-12-16 17:06:55.0 +00:00:00
geneknit	In favor	2025-12-16 23:41:17.0 +00:00:00
muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00
@lerhaupt	Pending
@hughesthe1st	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

Non-binding votes (1)

User	Vote	Timestamp
holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[git-vote]

Vote status

So far 50.00% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
4	0	0	4

Binding votes (4)

User	Vote	Timestamp
ToddSegal	In favor	2025-12-19 19:24:46.0 +00:00:00
darrelmiller	In favor	2025-12-16 17:06:55.0 +00:00:00
geneknit	In favor	2025-12-16 23:41:17.0 +00:00:00
muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00
@lerhaupt	Pending
@hughesthe1st	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

Non-binding votes (1)

User	Vote	Timestamp
holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[git-vote]

Vote status

So far 50.00% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
4	0	0	4

Binding votes (4)

User	Vote	Timestamp
ToddSegal	In favor	2025-12-19 19:24:46.0 +00:00:00
darrelmiller	In favor	2025-12-16 17:06:55.0 +00:00:00
geneknit	In favor	2025-12-16 23:41:17.0 +00:00:00
muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00
@lerhaupt	Pending
@hughesthe1st	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

Non-binding votes (1)

User	Vote	Timestamp
holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[git-vote]

Vote status

So far 50.00% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
4	0	0	4

Binding votes (4)

User	Vote	Timestamp
ToddSegal	In favor	2025-12-19 19:24:46.0 +00:00:00
darrelmiller	In favor	2025-12-16 17:06:55.0 +00:00:00
geneknit	In favor	2025-12-16 23:41:17.0 +00:00:00
muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00
@lerhaupt	Pending
@hughesthe1st	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

Non-binding votes (1)

User	Vote	Timestamp
holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[git-vote]

Vote status

So far 50.00% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
4	0	0	4

Binding votes (4)

User	Vote	Timestamp
ToddSegal	In favor	2025-12-19 19:24:46.0 +00:00:00
darrelmiller	In favor	2025-12-16 17:06:55.0 +00:00:00
geneknit	In favor	2025-12-16 23:41:17.0 +00:00:00
muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00
@lerhaupt	Pending
@hughesthe1st	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

Non-binding votes (1)

User	Vote	Timestamp
holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[git-vote]

Vote status

So far 50.00% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
4	0	0	4

Binding votes (4)

User	Vote	Timestamp
ToddSegal	In favor	2025-12-19 19:24:46.0 +00:00:00
darrelmiller	In favor	2025-12-16 17:06:55.0 +00:00:00
geneknit	In favor	2025-12-16 23:41:17.0 +00:00:00
muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00
@lerhaupt	Pending
@hughesthe1st	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

Non-binding votes (1)

User	Vote	Timestamp
holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[git-vote]

Vote status

So far 50.00% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
4	0	0	4

Binding votes (4)

User	Vote	Timestamp
ToddSegal	In favor	2025-12-19 19:24:46.0 +00:00:00
darrelmiller	In favor	2025-12-16 17:06:55.0 +00:00:00
geneknit	In favor	2025-12-16 23:41:17.0 +00:00:00
muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00
@lerhaupt	Pending
@hughesthe1st	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

Non-binding votes (1)

User	Vote	Timestamp
holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[git-vote]

Vote status

So far 50.00% of the users with binding vote are in favor and 0.00% are against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
4	0	0	4

Binding votes (4)

User	Vote	Timestamp
ToddSegal	In favor	2025-12-19 19:24:46.0 +00:00:00
darrelmiller	In favor	2025-12-16 17:06:55.0 +00:00:00
geneknit	In favor	2025-12-16 23:41:17.0 +00:00:00
muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00
@lerhaupt	Pending
@hughesthe1st	Pending
@000-000-000-000-000	Pending
@SivaNSAP	Pending

Non-binding votes (1)

User	Vote	Timestamp
holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[git-vote]

Vote closed

The vote passed! 🎉

62.50% of the users with binding vote were in favor and 0.00% were against (passing threshold: 51%).

Summary

In favor	Against	Abstain	Not voted
5	0	0	3

Binding votes (5)

User	Vote	Timestamp
@SivaNSAP	In favor	2026-01-13 16:13:40.0 +00:00:00
@ToddSegal	In favor	2025-12-19 19:24:46.0 +00:00:00
@darrelmiller	In favor	2025-12-16 17:06:55.0 +00:00:00
@geneknit	In favor	2025-12-16 23:41:17.0 +00:00:00
@muscariello	In favor	2025-12-11 21:40:15.0 +00:00:00

Non-binding votes (1)

User	Vote	Timestamp
@holtskinner	In favor	2025-12-11 15:29:29.0 +00:00:00

[xui-will]

This proposal introduces a breaking change at the gRPC/protobuf level, and the associated cost in terms of client updates, regressions, and debugging should not be overlooked.

In protobuf, only field numbers are preserved on the wire, not the field definitions. Changing the type of an existing field creates a compatibility gap: a newer client interacting with an older agent (or vice versa) would be unable to reliably interpret DataPart, effectively breaking interoperability of one of the most heavily used field of the whole protocol.

Alternative solutions should be considered. For instance, and safer pattern would be to introduce a new field and deprecate the existing one rather than changing it in place.

Also, FWIW: We have made a different proposal to allow usage of the gRPC type Any which is even more powerful.
I would like to have our proposal considered in conjunction to this PR, as I feel it's either complementary or redundant. c.f. #1300

[darrelmiller]

@xui-will The latest iteration of the thinking about changes to the Part type are documented in this comment here #1255 (comment)

We are moving to a v1.0, which is a breaking change from v0.3. This is an opportunity we need to take before we release v1 and we will not want to make any breaking changes for hopefully a long time.

My understanding of Any is that it enables passing any gRPC type, but it expects the gRPC type identifier to be communicated. This is not simple to support with other protocol bindings.

[muscariello]

LGTM

[Tehsmash]

@darrelmiller @muscariello I think we can close this in favor of Darrel's PR which refactors Part completely: #1363. This PR switches content.Data to a Value so that it supports arrays / other json primitives.