Retro Diffusion Pixel Art

Start Async Generation

start_inference_job

Start a generation as an async job (POST /v2/inferences with async=true) and return a task_id.

Recommended for advanced animations (rd_advanced_animation__*), other animation styles, and batches — they run for tens of seconds and can outlive a synchronous MCP call. Poll the returned task_id with get_inference_job roughly every 2-5 seconds.

Input Schema

TableJSON Schema

Name	Required	Description
`seed`	No	Seed for reproducible results; reuse the same seed to iterate on one composition.
`width`	Yes	Output width in pixels. Each style enforces its own limits; check list_available_styles or get_style_usage. Genre-native sizes per item: Minecraft 16; items/icons/props 32-64; character sprites 16-48 retro or 96-128 showcase; tiles 16-32; portraits 96-128; full scenes 256 (RD Pro's max; 16:9 scenes = 256x144 — pixel art integer-upscales losslessly).
`height`	Yes	Output height in pixels. Each style enforces its own limits; check list_available_styles or get_style_usage.
`prompt`	Yes	Describe the SUBJECT only, richly and concretely ('a squat round flask of glowing crimson liquid, cork stopper, bright highlight on the upper-left rim' beats 'a potion'). Never write 'pixel art' — the selected style handles all rendering. For standalone assets, state a flat background color that contrasts the subject (default 'on a plain white background') and pair with remove_bg=true; never write 'transparent background' (that is remove_bg's job), and never leave the background unstated (it drifts to drab dark gray). Scenes instead describe their real environment. For rd_advanced_animation__rotate the prompt is only an optional hint describing the uploaded subject — a few words or an empty string.
`tile_x`	No	Make the result tile seamlessly on the horizontal axis.
`tile_y`	No	Make the result tile seamlessly on the vertical axis.
`strength`	No	How strongly to change input_image, 0-1 (default 0.75). Lower values keep more of the original.
`remove_bg`	No	Remove the background for transparent output. Use true for standalone assets and pair it with a stated contrasting background in the prompt ('on a plain white background') — removal works best on flat contrasting backdrops. Animations inherit the start frame's transparency automatically.
`num_images`	No	How many images to generate in one batch; a batch produces varied takes of one prompt (the right way to get N distinct items as individually usable images — never pack N items into a single sheet/grid image unless a sheet IS the deliverable). Style-specific maximums apply.
`rd_api_key`	No	RetroDiffusion API key (rdpk-...) for this call only; overrides session or header auth.
`input_image`	No	Base64 PNG used as the main source image for edits, variations, tilesets, animations, or styles that require a starting frame. Raw base64 or a data URL. Send the NATIVE-resolution image: an upscaled display copy (e.g. a 96px sprite exported at 4x = 384px) exceeds style ranges and gets rejected — downscale to the true pixel grid first. For advanced animations the frame's dimensions must equal width/height, and sprites whose opaque pixels touch the canvas edge animate badly (pad onto a larger transparent canvas first, e.g. 48x48 content onto 64x64).
`extra_prompt`	No	Secondary prompt for styles that use one (e.g. the transition texture in advanced tilesets).
`prompt_style`	Yes	Style id from list_available_styles (e.g. 'rd_fast__default', 'rd_pro__isometric', or a custom 'user__...' style).
`input_palette`	No	Base64 image of a color palette; output colors are constrained to it.
`upload_outputs`	No	Host outputs and return URLs in output_urls (recommended for MCP clients) instead of only base64 payloads.
`frames_duration`	No	Animation frame count for animation styles: 4, 6, 8, 10, 12, or 16. Pick deliberately: 8 is the sweet spot for loops (walking, idle), 6 for a snappy single action, 10-12 for flowing ambient motion. Ignored by rd_advanced_animation__rotate (always 8 views).
`timeout_seconds`	No	Read-timeout override in seconds for this call; increase for animations or large batches.
`reference_images`	No	Extra per-inference guidance images (base64), only for styles where supports_reference_images is true. Not for defining custom styles.
`extra_input_image`	No	Second base64 input image for styles that use one (e.g. the second texture in rd_tile__tileset_advanced).
`return_pre_palette`	No	Also return the render from before palette constraints were applied.
`return_spritesheet`	No	For animation styles: return a PNG sprite sheet instead of a GIF (for rd_advanced_animation__rotate, the 3x3 direction sheet whose views face the center).
`return_non_bg_removed`	No	Also return the render from before background removal was applied.
`upscale_output_factor`	No	Integer upscale factor for the output image; 1 returns the native pixel size.
`bypass_prompt_expansion`	No	Skip the automatic LLM prompt enrichment and use the prompt verbatim.
`include_downloadable_data`	No	Include extra structured assets when available (e.g. tileset atlas JSON, animation frame data).

Output Schema

TableJSON Schema

Name	Required	Description	Default
No arguments

Schema Changelog

Changes observed during successful MCP inspections.

Changed3 schema fields changedSep 14, 2026

changedInput schema / properties / frames_duration / description

Previous value: -"Animation frame count for animation styles: 4, 6, 8, 10, 12, or 16. Pick deliberately: 8 is the sweet spot for loops (walking, idle), 6 for a snappy single action, 10-12 for flowing ambient motion."New value: +"Animation frame count for animation styles: 4, 6, 8, 10, 12, or 16. Pick deliberately: 8 is the sweet spot for loops (walking, idle), 6 for a snappy single action, 10-12 for flowing ambient motion. Ignored by rd_advanced_animation__rotate (always 8 views)."

changedInput schema / properties / prompt / description

Previous value: -"Describe the SUBJECT only, richly and concretely ('a squat round flask of glowing crimson liquid, cork stopper, bright highlight on the upper-left rim' beats 'a potion'). Never write 'pixel art' — the selected style handles all rendering. For standalone assets, state a flat background color that contrasts the subject (default 'on a plain white background') and pair with remove_bg=true; never write 'transparent background' (that is remove_bg's job), and never leave the background unstated (it drifts to drab dark gray). Scenes instead describe their real environment."New value: +"Describe the SUBJECT only, richly and concretely ('a squat round flask of glowing crimson liquid, cork stopper, bright highlight on the upper-left rim' beats 'a potion'). Never write 'pixel art' — the selected style handles all rendering. For standalone assets, state a flat background color that contrasts the subject (default 'on a plain white background') and pair with remove_bg=true; never write 'transparent background' (that is remove_bg's job), and never leave the background unstated (it drifts to drab dark gray). Scenes instead describe their real environment. For rd_advanced_animation__rotate the prompt is only an optional hint describing the uploaded subject — a few words or an empty string."

changedInput schema / properties / return_spritesheet / description

Previous value: -"For animation styles: return a PNG sprite sheet instead of a GIF."New value: +"For animation styles: return a PNG sprite sheet instead of a GIF (for rd_advanced_animation__rotate, the 3x3 direction sheet whose views face the center)."

Changed6 schema fields changedAug 22, 2026

changedInput schema / properties / frames_duration / description

Previous value: -"Animation frame count for animation styles: 4, 6, 8, 10, 12, or 16."New value: +"Animation frame count for animation styles: 4, 6, 8, 10, 12, or 16. Pick deliberately: 8 is the sweet spot for loops (walking, idle), 6 for a snappy single action, 10-12 for flowing ambient motion."

changedInput schema / properties / input_image / description

Previous value: -"Base64 PNG used as the main source image for edits, variations, tilesets, animations, or styles that require a starting frame. Raw base64 or a data URL."New value: +"Base64 PNG used as the main source image for edits, variations, tilesets, animations, or styles that require a starting frame. Raw base64 or a data URL. Send the NATIVE-resolution image: an upscaled display copy (e.g. a 96px sprite exported at 4x = 384px) exceeds style ranges and gets rejected — downscale to the true pixel grid first. For advanced animations the frame's dimensions must equal width/height, and sprites whose opaque pixels touch the canvas edge animate badly (pad onto a larger transparent canvas first, e.g. 48x48 content onto 64x64)."

changedInput schema / properties / num_images / description

Previous value: -"How many images to generate in one batch. Style-specific maximums apply."New value: +"How many images to generate in one batch; a batch produces varied takes of one prompt (the right way to get N distinct items as individually usable images — never pack N items into a single sheet/grid image unless a sheet IS the deliverable). Style-specific maximums apply."

changedInput schema / properties / prompt / description

Previous value: -"Describe the SUBJECT only (e.g. 'a knight resting by a campfire'). Never write 'pixel art' — the selected style handles all rendering."New value: +"Describe the SUBJECT only, richly and concretely ('a squat round flask of glowing crimson liquid, cork stopper, bright highlight on the upper-left rim' beats 'a potion'). Never write 'pixel art' — the selected style handles all rendering. For standalone assets, state a flat background color that contrasts the subject (default 'on a plain white background') and pair with remove_bg=true; never write 'transparent background' (that is remove_bg's job), and never leave the background unstated (it drifts to drab dark gray). Scenes instead describe their real environment."

changedInput schema / properties / remove_bg / description

Previous value: -"Remove the background for transparent output."New value: +"Remove the background for transparent output. Use true for standalone assets and pair it with a stated contrasting background in the prompt ('on a plain white background') — removal works best on flat contrasting backdrops. Animations inherit the start frame's transparency automatically."

changedInput schema / properties / width / description

Previous value: -"Output width in pixels. Each style enforces its own limits; check list_available_styles or get_style_usage."New value: +"Output width in pixels. Each style enforces its own limits; check list_available_styles or get_style_usage. Genre-native sizes per item: Minecraft 16; items/icons/props 32-64; character sprites 16-48 retro or 96-128 showcase; tiles 16-32; portraits 96-128; full scenes 256 (RD Pro's max; 16:9 scenes = 256x144 — pixel art integer-upscales losslessly)."

First observedJul 10, 2026

TDQS

A4.3/5.0

Behavior4/5

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

Annotations already declare readOnlyHint=false, idempotentHint=false, openWorldHint=true, destructiveHint=false, so the safety profile is covered; the description adds genuine behavioral context on async execution, the returned task_id, and the polling cadence. It stops short of warning that repeated calls create duplicate jobs (relevant given idempotentHint=false) or addressing auth/cost, so it earns a 4 rather than a 5.

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

Conciseness4/5

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

Two tight sentences with no waste; the endpoint and return value are front-loaded ahead of the recommendation. It is slightly under-explained for a 25-parameter tool, but nothing is filler.

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 no explanation, and the description still supplies the key workflow fact (task_id plus polling interval). For a 25-param async tool with 4 required params, this covers what an agent needs to invoke it correctly, though it could note that the job continues server-side after the call returns.

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 100% across all 25 parameters, so the schema already carries the full parameter burden, including style limits, seed reuse, and animation frame counts. The description adds no per-parameter guidance of its own, making the baseline 3 correct.

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, and mechanism: 'Start a generation as an async job (POST /v2/inferences with async=true) and return a task_id.' This clearly separates it from the sibling create_inference (synchronous generation) without needing to open either schema.

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?

Explicitly names the cases that select this tool (advanced animations rd_advanced_animation__*, other animation styles, batches), explains why (they run for tens of seconds and can outlive a synchronous MCP call), and gives the follow-up procedure ('poll the returned task_id with get_inference_job roughly every 2-5 seconds'). Nothing is left to inference.

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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