spawn_play_input

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

No annotations exist, so the description carries the full burden and does well: it discloses the one-time canvas-center click for keyboard focus, the batching behavior without stray clicks, and the cross-origin iframe limitation. Minor inconsistency: the description says to call spawn_play_screenshot after, but the schema has screenshot=true by default; this is not a direct contradiction but could cause slight confusion.

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 with a clear purpose: definition, focus behavior, and UI workflow. It is front-loaded with the primary action and contains no fluff; every sentence earns its place.

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?

Given the tool's complexity (5 parameters, 7 action types), the description covers the critical behavioral context: the one-time click, the UI-click method, and the follow-up screenshot step. It does not explicitly describe return values, but since the primary output is a visual screenshot and schema handles details, this is adequate. Could mention the screenshot parameter indirectly but not necessary.

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 descriptions cover 100% of parameters, so baseline is 3. The description adds value beyond the schema by explaining the canvas-center click behavior (relevant for click coordinates and refocus), and the pixel-from-screenshot workflow for x/y, improving practical understanding of the actions parameter and coordinate fields.

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?

Description clearly states 'Send keyboard/mouse actions to the play session' with a specific verb and resource. It also distinguishes itself by noting it is the ONLY way to click the game's UI, separating it from sibling tools like spawn_play_eval.

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?

Provides explicit when-to-use guidance by explaining that spawn_play_eval cannot reach the cross-origin UI iframe, so this tool is required. It also gives a concrete workflow: screenshot first, read button coordinates, then click those positions, and suggests a follow-up with spawn_play_screenshot.

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