capture_canvas

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

With no annotations, the description carries the full burden and does so thoroughly. It discloses non-cached rendering, full page load waiting, WebKit rendering, performance cost, default image count, and the ability to target specific routes—important behavioral traits beyond what the schema shows.

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?

The description is well-structured with clear USAGE and CONSTRAINTS sections. Every sentence adds practical value—no filler or redundancy—and the format makes it easy for an agent to scan and apply the guidance.

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?

The tool is fully contextualized despite having no output schema: it covers purpose, performance, constraints, parameter usage, alternatives, and expected output format. The information is sufficient for an agent to decide when and how to invoke the tool correctly.

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 already 100%, but the description adds meaningful context: the default limit of 3, the benefit of passing specific route IDs for speed and context savings, and the source of route IDs (list_routes/add_route). This goes well beyond the raw schema definitions.

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 clearly states the tool captures fresh screenshots of routes on the Design Canvas, with specific details like triggering a new render and returning images. It distinguishes itself from sibling tools (list_routes, add_route, remove_route) by focusing on visual verification rather than route management.

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?

Explicit usage guidance is provided: use after making code changes for visual verification, avoid speculative calls due to cost, and pass specific route IDs to save time/context. It also names Playwright as the alternative for cross-browser verification, giving clear when-to-use and when-not-to-use direction.

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