Generate cover and thumbnail

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

Goes well beyond the annotations (destructiveHint/openWorldHint) by naming exactly what gets written, that existing cover/thumb files are refused unless overwrite:true, that uploads replace the listing's current images, and that the game path requires login. It also discloses the return payload: file paths plus the cover as an image.

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

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

Three sentences, each load-bearing, with the core action front-loaded before side effects and routing. Dense nested parentheticals (e.g. the screenshot example and the overwrite caveat) slightly slow scanning but carry genuine information.

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

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

With no output schema, the description supplies the return shape itself (paths plus cover image), plus overwrite semantics, login requirement, and upload side effects. Nothing an agent needs to invoke this safely and correctly is missing.

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

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

Schema coverage is 100%, so baseline is 3, and the description adds real meaning: an example screenshot value tied to gamealia_run_autotest, the outDir default behavior, and the consequence of overwrite:true. It stops short of clarifying formats or constraints on title beyond what the schema states.

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

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

States a specific verb and concrete outputs: makes a 1200x630 cover and 512x512 thumbnail from a gameplay screenshot, center-cropped with the title on a gradient. It also names the downstream siblings (gamealia_create_game, gamealia_update_listing), so an agent can place it precisely in the workflow.

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

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

Explicitly branches usage: omit `game` for local-only generation, pass `game` (requires login) to also upload and replace listing images, and otherwise hand the resulting files to gamealia_create_game or gamealia_update_listing. When-to-use, when-not, and alternatives are all present.

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