a2a-buffer

get_artifact

Read-onlyIdempotent

WHEN: You need manifest metadata or a download URL for a registered artifact. DO: GET /api/v1/artifacts/{id}. Returns media_type, byte_size, RFC 9530 digest, created_at, and a download_url (5-minute redirect). No API key. DON'T: Assume bytes are inlined; follow download_url and verify Content-Digest. NEXT: GET download_url or register_artifact for new bytes.

Input Schema

Name	Required	Description	Default
`id`	Yes	Artifact UUID from register_artifact.

Output Schema

Name	Required	Description
`status`	Yes	pending until POST /complete, then active.
`task_id`	No	Linked work-contract UUID when present.
`byte_size`	Yes	Declared object size in bytes.
`created_at`	Yes	ISO-8601 creation timestamp.
`expires_at`	Yes	ISO-8601 manifest expiry.
`media_type`	Yes	IANA media type.
`provenance`	No	Publisher provenance object.
`artifact_id`	Yes	Artifact manifest UUID.
`download_url`	Yes	Short-lived content URL (about 5 minutes).
`publisher_id`	Yes	Publisher agent id.
`digest_sha256`	Yes	RFC 9530 digest_sha256 manifest hash.

Schema Changelog

Changes observed during successful MCP inspections.

Changed15 schema fields changedOct 22, 2026

removedOutput schema / additionalProperties
```
Removed value: -false
```

addedOutput schema / properties / artifact_id

Added value: +{
+  "description": "Artifact manifest UUID.",
+  "title": "Artifact Id",
+  "type": "string"
+}

addedOutput schema / properties / created_at

Added value: +{
+  "description": "ISO-8601 creation timestamp.",
+  "title": "Created At",
+  "type": "string"
+}

removedOutput schema / properties / digest

Removed value: -{
-  "description": "RFC 9530 digest_sha256 manifest hash.",
-  "title": "Digest",
-  "type": "string"
-}

addedOutput schema / properties / digest_sha256

Added value: +{
+  "description": "RFC 9530 digest_sha256 manifest hash.",
+  "title": "Digest Sha256",
+  "type": "string"
+}

changedOutput schema / properties / download_url / description

Previous value: -"Short-lived redirect URL for GET (about 5 minutes)."New value: +"Short-lived content URL (about 5 minutes)."

addedOutput schema / properties / expires_at

Added value: +{
+  "description": "ISO-8601 manifest expiry.",
+  "title": "Expires At",
+  "type": "string"
+}

removedOutput schema / properties / id

Removed value: -{
-  "description": "Artifact UUID.",
-  "title": "Id",
-  "type": "string"
-}

addedOutput schema / properties / media_type

Added value: +{
+  "description": "IANA media type.",
+  "title": "Media Type",
+  "type": "string"
+}

removedOutput schema / properties / mime_type

Removed value: -{
-  "description": "IANA media type (media_type in JSON responses).",
-  "title": "Mime Type",
-  "type": "string"
-}

addedOutput schema / properties / provenance

Added value: +{
+  "additionalProperties": true,
+  "description": "Publisher provenance object.",
+  "title": "Provenance",
+  "type": "object"
+}

addedOutput schema / properties / publisher_id

Added value: +{
+  "description": "Publisher agent id.",
+  "title": "Publisher Id",
+  "type": "string"
+}

addedOutput schema / properties / status

Added value: +{
+  "description": "pending until POST /complete, then active.",
+  "title": "Status",
+  "type": "string"
+}

addedOutput schema / properties / task_id

Added value: +{
+  "anyOf": [
+    {
+      "type": "string"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "default": null,
+  "description": "Linked work-contract UUID when present.",
+  "title": "Task Id"
+}

changedOutput schema / required

Previous value: -[
-  "id",
-  "mime_type",
-  "byte_size",
-  "digest",
-  "download_url"
-]New value: +[
+  "artifact_id",
+  "publisher_id",
+  "media_type",
+  "byte_size",
+  "digest_sha256",
+  "status",
+  "created_at",
+  "expires_at",
+  "download_url"
+]

Changed6 schema fields changedOct 19, 2026

changedInput schema / properties / id / description

Previous value: -"Artifact identifier."New value: +"Artifact UUID from register_artifact."

addedInput schema / properties / id / examples

Added value: +[
+  "550e8400-e29b-41d4-a716-446655440000"
+]

addedInput schema / properties / id / maxLength
```
Added value: +36
```
addedInput schema / properties / id / minLength
```
Added value: +36
```
addedInput schema / properties / id / title
```
Added value: +"Id"
```

changedOutput schema / (root)

Previous value: -nullNew value: +{
+  "additionalProperties": false,
+  "properties": {
+    "byte_size": {
+      "description": "Declared object size in bytes.",
+      "title": "Byte Size",
+      "type": "integer"
+    },
+    "digest": {
+      "description": "RFC 9530 digest_sha256 manifest hash.",
+      "title": "Digest",
+      "type": "string"
+    },
+    "download_url": {
+      "description": "Short-lived redirect URL for GET (about 5 minutes).",
+      "title": "Download Url",
+      "type": "string"
+    },
+    "id": {
+      "description": "Artifact UUID.",
+      "title": "Id",
+      "type": "string"
+    },
+    "mime_type": {
+      "description": "IANA media type (media_type in JSON responses).",
+      "title": "Mime Type",
+      "type": "string"
+    }
+  },
+  "required": [
+    "id",
+    "mime_type",
+    "byte_size",
+    "digest",
+    "download_url"
+  ],
+  "type": "object"
+}

First observedOct 19, 2026

TDQS

A4.7/5.0

Behavior5/5

Does the description disclose side effects, auth requirements, rate limits, or destructive behavior?

Annotations already cover read-only/idempotent, and the description adds genuinely new behavior: no API key required, the download_url is a 5-minute redirect, bytes are not inlined, and the caller should verify Content-Digest. These are non-obvious operational facts not derivable from structured fields.

Agents need to know what a tool does to the world before calling it. Descriptions should go beyond structured annotations to explain consequences.

Conciseness5/5

Is the description appropriately sized, front-loaded, and free of redundancy?

WHEN/DO/DON'T/NEXT framing is front-loaded and scannable, with every clause carrying distinct information. No filler sentences.

Shorter descriptions cost fewer tokens and are easier for agents to parse. Every sentence should earn its place.

Completeness5/5

Given the tool's complexity, does the description cover enough for an agent to succeed on first attempt?

For a one-parameter read tool with annotations and an output schema, this covers purpose, endpoint, response fields, auth, redirect lifetime, and the follow-up step. Nothing an agent needs to invoke it correctly is missing.

Complex tools with many parameters or behaviors need more documentation. Simple tools need less. This dimension scales expectations accordingly.

Parameters3/5

Does the description clarify parameter syntax, constraints, interactions, or defaults beyond what the schema provides?

Schema coverage is 100% and the single id parameter is already documented as a UUID from register_artifact, so the description correctly defers. It adds no format or validation detail beyond the schema, so the baseline 3 applies.

Input schemas describe structure but not intent. Descriptions should explain non-obvious parameter relationships and valid value ranges.

Purpose5/5

Does the description clearly state what the tool does and how it differs from similar tools?

States a specific verb+resource (fetch artifact manifest metadata / download URL) and pins the exact endpoint. Distinguishes it from register_artifact by scoping it to retrieval of already-registered artifacts.

Agents choose between tools based on descriptions. A clear purpose with a specific verb and resource helps agents select the right tool.

Usage Guidelines5/5

Does the description explain when to use this tool, when not to, or what alternatives exist?

Explicit WHEN clause plus a DON'T that rules out a common misuse (assuming inlined bytes), and a NEXT that routes to register_artifact for new bytes. An agent knows both when to call it and what to do after.

Agents often have multiple tools that could apply. Explicit usage guidance like "use X instead of Y when Z" prevents misuse.

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