Kuro

Retry a failed generation

regenerate_generation

Retry a generation that failed, on the same recipe. Only a failed one can be retried — to make another version of something that worked, call the generate tool again. The new attempt joins the original's retry group.

Tool call template

Replace each placeholder with a value matching the input schema. Only required parameters are included; add optional parameters as needed.

{
  "id": 1,
  "jsonrpc": "2.0",
  "method": "tools/call",
  "params": {
    "arguments": {
      "generation_id": "<generation_id>"
    },
    "name": "regenerate_generation"
  }
}

Input Schema

Name	Required	Description	Default
`generation_id`	Yes

Output Schema

Name	Required	Description	Default
`message`	Yes
`generation`	Yes	One image, clip, voice-over or piece of music.

Schema Changelog

Changes observed during successful MCP inspections.

Changed20 schema fields changedNov 4, 2026

addedOutput schema / properties / generation / description

Added value: +"One image, clip, voice-over or piece of music."

addedOutput schema / properties / generation / properties / app_url / description
```
Added value: +"Opens it in the app."
```
addedOutput schema / properties / generation / properties / aspect_ratio / description
```
Added value: +"Null for audio."
```
addedOutput schema / properties / generation / properties / created_at / format
```
Added value: +"date-time"
```

addedOutput schema / properties / generation / properties / credits

Added value: +{
+  "description": "Credits charged. Zero when your own provider key or the free allowance paid.",
+  "type": [
+    "number",
+    "null"
+  ]
+}

removedOutput schema / properties / generation / properties / credits_cost
```
Removed value: -{
-  "type": [
-    "number",
-    "null"
-  ]
-}
```
addedOutput schema / properties / generation / properties / error / description
```
Added value: +"Why it failed. Null otherwise."
```
removedOutput schema / properties / generation / properties / generation_id
```
Removed value: -{
-  "format": "uuid",
-  "type": "string"
-}
```

addedOutput schema / properties / generation / properties / id

Added value: +{
+  "format": "uuid",
+  "type": "string"
+}

removedOutput schema / properties / generation / properties / kind

Removed value: -{
-  "enum": [
-    "image",
-    "video",
-    "audio",
-    "tool"
-  ],
-  "type": "string"
-}

addedOutput schema / properties / generation / properties / model / description
```
Added value: +"The model id it was made with (`GET /v1/models`)."
```

addedOutput schema / properties / generation / properties / object

Added value: +{
+  "const": "generation",
+  "type": "string"
+}

addedOutput schema / properties / generation / properties / output_url / description

Added value: +"The finished file, once `ready`. A signed link that works for about an hour; read the generation again for a fresh one."

addedOutput schema / properties / generation / properties / paid_by / description

Added value: +"Who paid: \"credits\", \"house\" (the free allowance), \"server\" (a server that charges nothing), or the vendor of your own key (\"replicate\", \"fal\", …)."

addedOutput schema / properties / generation / properties / ready_in_seconds / description

Added value: +"Roughly how long an unfinished generation has left; 0 means past its usual time."

addedOutput schema / properties / generation / properties / recipe_id

Added value: +{
+  "anyOf": [
+    {
+      "$ref": "#/properties/generation/properties/id"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "description": "The recipe it was made with, if any."
+}

addedOutput schema / properties / generation / properties / status / description
```
Added value: +"`ready` and `failed` are final."
```

addedOutput schema / properties / generation / properties / thumbnail_url

Added value: +{
+  "anyOf": [
+    {
+      "$ref": "#/properties/generation/properties/output_url/anyOf/0"
+    },
+    {
+      "type": "null"
+    }
+  ],
+  "description": "A small still of the result, for a grid. Null for audio and while it works."
+}

addedOutput schema / properties / generation / properties / type

Added value: +{
+  "description": "What was made. New values may be added; treat an unknown one as opaque.",
+  "enum": [
+    "image",
+    "clip",
+    "voiceover",
+    "music",
+    "tool"
+  ],
+  "type": "string"
+}

changedOutput schema / properties / generation / required

Previous value: -[
-  "generation_id",
-  "kind",
-  "status",
-  "model",
-  "prompt",
-  "aspect_ratio",
-  "refined_from",
-  "caption_style",
-  "output_url",
-  "credits_cost",
-  "paid_by",
-  "error",
-  "vendor_phase",
-  "stalled",
-  "ready_in_seconds",
-  "created_at",
-  "app_url"
-]New value: +[
+  "object",
+  "id",
+  "type",
+  "status",
+  "model",
+  "prompt",
+  "aspect_ratio",
+  "output_url",
+  "thumbnail_url",
+  "credits",
+  "paid_by",
+  "error",
+  "ready_in_seconds",
+  "recipe_id",
+  "created_at",
+  "app_url",
+  "refined_from",
+  "caption_style",
+  "vendor_phase",
+  "stalled"
+]

Changed2 schema fields changedOct 26, 2026

addedOutput schema / properties / generation / properties / paid_by
```
Added value: +{
+  "type": [
+    "string",
+    "null"
+  ]
+}
```

changedOutput schema / properties / generation / required

Previous value: -[
-  "generation_id",
-  "kind",
-  "status",
-  "model",
-  "prompt",
-  "aspect_ratio",
-  "refined_from",
-  "caption_style",
-  "output_url",
-  "credits_cost",
-  "error",
-  "vendor_phase",
-  "stalled",
-  "ready_in_seconds",
-  "created_at",
-  "app_url"
-]New value: +[
+  "generation_id",
+  "kind",
+  "status",
+  "model",
+  "prompt",
+  "aspect_ratio",
+  "refined_from",
+  "caption_style",
+  "output_url",
+  "credits_cost",
+  "paid_by",
+  "error",
+  "vendor_phase",
+  "stalled",
+  "ready_in_seconds",
+  "created_at",
+  "app_url"
+]

Changed2 schema fields changedOct 21, 2026

addedOutput schema / properties / generation / properties / ready_in_seconds
```
Added value: +{
+  "type": [
+    "number",
+    "null"
+  ]
+}
```

changedOutput schema / properties / generation / required

Previous value: -[
-  "generation_id",
-  "kind",
-  "status",
-  "model",
-  "prompt",
-  "aspect_ratio",
-  "refined_from",
-  "caption_style",
-  "output_url",
-  "credits_cost",
-  "error",
-  "vendor_phase",
-  "stalled",
-  "created_at",
-  "app_url"
-]New value: +[
+  "generation_id",
+  "kind",
+  "status",
+  "model",
+  "prompt",
+  "aspect_ratio",
+  "refined_from",
+  "caption_style",
+  "output_url",
+  "credits_cost",
+  "error",
+  "vendor_phase",
+  "stalled",
+  "ready_in_seconds",
+  "created_at",
+  "app_url"
+]

First observedOct 15, 2026

TDQS

A4.2/5.0

Behavior4/5

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

Annotations flag this as a non-read-only, non-destructive, non-idempotent write, and the description adds real context beyond them: the retry is bound to the original recipe and the new attempt is linked to the original via a retry group, which tells the agent results are correlated rather than independent. It does not say whether retrying consumes additional credits or produces a new generation id, which are the two operational facts an agent would most want.

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?

Three short sentences: purpose first, the eligibility restriction and its alternative second, and the retry-group behavior last. No redundant restatement of the title or the tool name.

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

Completeness4/5

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

An output schema exists, so return values need not be described, and annotations cover the safety profile; the description fills in the eligibility rule and the retry-group semantics, which are the non-obvious parts. The residual gap is the ambiguous reference to "the generate tool" in a catalog with six generate_* siblings.

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 description coverage is 0%, so the schema names generation_id (uuid) with no explanation; the description partially compensates by establishing that the id must belong to a failed generation. It says nothing about what the identifier refers to structurally (the failed attempt, not the retry group or the recipe), so a single unambiguous parameter is left to inference.

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 (retry), a specific resource (a generation), and a scoping constraint (failed only, same recipe), plus explicitly contrasts itself with another tool. An agent can distinguish this from generate_with_recipe, retry_workflow_run, or update_generation without opening any schema.

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

Usage Guidelines4/5

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

Gives both a when-to-use condition ("a generation that failed") and a when-not/alternative ("to make another version of something that worked, call the generate tool again"). The only gap is that "the generate tool" is not an exact sibling name — the catalog has generate_with_recipe, generate_clip, generate_image, generate_music — so the agent must infer which one is meant.

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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