Export screenshots

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

Annotations already declare readOnlyHint=false and destructiveHint=false, yet the description adds value beyond them: it says files land in the app's exports folder, that the call returns the file path, and that rendering must already be complete. It does not cover overwrite behavior for a pre-existing export file, which would be the remaining gap for a write tool.

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 short sentences, front-loaded with the action and destination, followed by layout options, return value, and prerequisite. Dense and nearly waste-free, with only minor awkwardness in framing 'fastlane' as a zip-like output.

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?

For a two-parameter write tool with no output schema, the description supplies the destination, the return value, the layout semantics, and the rendering prerequisite. The only missing piece is behavior when an export already exists, a minor omission given the low complexity.

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 would be 3, but the description adds real meaning to the layout enum by explaining that 'zip' produces a folder per locale plus manifest.json and 'fastlane' produces deliver/supply folders. That is exactly the detail an agent needs to pick a value, not a restatement of the schema.

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?

The description uses a specific verb plus resource ('Write the complete rendered set as a zip into the app's exports folder') and clearly distinguishes this tool from siblings like screenshots_render or screenshots_upload by naming the output artifact and destination.

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?

It states an important precondition — 'Every screenshot must be rendered for the current design' — which tells the agent when this tool will succeed versus when screenshots_render must run first. It does not explicitly name that sibling as a fallback step, so usage guidance is strong but not fully explicit about alternatives.

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