spawnpop

Generate a game sprite sheet

generate_sprite_sheet

Idempotent

Spends credits (180, plus 50 for each extra animation, at most 2). Draws one character from a description in a chosen style with idle, run and attack animations and delivers the sheet, GIFs, frames and JSON via get_sprite_status. confirmCredits must equal the price; the same requestId returns the same order and charges nothing. Only one paid sprite order is open per account at a time. Without an API key nothing is spent: you get the price and links for the user.

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": {
      "description": "<description>",
      "style": "<style>"
    },
    "name": "generate_sprite_sheet"
  }
}

Input Schema

Name	Required	Description
`style`	Yes
`extras`	No
`fromRunId`	No	A finished web preview of the same character: keeps its character and idle sheet, so only the rest is drawn.
`requestId`	No	Required with an API key. A new one for each new purchase, the same one to retry.
`description`	Yes
`confirmCredits`	No	The exact price you showed the user. Required with an API key.

Schema Changelog

Changes observed during successful MCP inspections.

AddedOct 27, 2026

TDQS

A4.6/5.0

Behavior5/5

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

Adds substantial behavior beyond annotations: credit cost formula (180 + 50 per extra, max 2), the requestId idempotency contract (same id = same order, no charge), the one-open-order-per-account limit, and free dry-run behavior without an API key. These are the exact traits idempotentHint=true implies but does not explain.

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?

Four dense sentences, front-loaded with the cost impact. Minor redundancy with the schema (the 'at most 2' cap repeats maxItems), but 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?

No output schema exists, and the description explicitly says what is produced (sheet, GIFs, frames, JSON) and how to collect it via get_sprite_status. Pricing, retry, and auth behavior are all covered, so an agent has what it needs to call this safely.

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

Parameters4/5

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

Schema coverage is 50%, and the description fills key gaps: extras pricing and the 2-item cap, confirmCredits equality requirement, and requestId reuse semantics. It adds nothing about 'style' choices or the 'description' text itself, which the schema only partially covers.

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 and resource: draws one character from a description in a chosen style with idle/run/attack animations, and names how output is retrieved (get_sprite_status). This clearly distinguishes it from retrieval siblings like get_sprite_status and get_files.

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 concrete preconditions: confirmCredits must equal the price, one paid order open per account, and without an API key you only get price and links. It does not differentiate from the sibling 'generate' or 'draft' tools, so the alternative selection is left implicit.

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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