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

Annotations declare a non-read-only, non-open-world, non-destructive write, and the description adds substantive context beyond them: the HTML is 'temporarily uploaded to TheySaid', the response shape {uploadId, uploadUrl, expiresInSeconds, nextStep}, the required content form (text/html, inlined CSS/JS, absolute CDN URLs), and the explicit disclaimer that it does not start a test.

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?

Front-loaded with purpose, then sequencing via 'Then:' and 'This tool does not start a test'. It is long and includes mild redundancy — the point that live apps need a public URL is made twice — but nearly every sentence carries actionable information given the tool's complexity.

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 an output schema exists, the return-value explanation is a bonus rather than a necessity, and the definition still covers the full workflow (upload, check, propose/relaunch), the fallback tool, and the static-vs-live boundary. Nothing an agent needs to invoke it 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?

With zero parameters, the baseline is 4. The description usefully documents the upload contract that the agent must fulfill (single PUT to uploadUrl, content types, inlining rules), even though this concerns the workflow rather than named parameters.

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 resource — 'Creates an upload slot for a self-contained design (HTML)' — and immediately scopes the purpose to enabling a usability test. It also distinguishes itself from the similarly named sibling upload_design_snapshot by positioning that tool as the fallback when the upload host is blocked.

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 when-to-use ('designs without a durable public URL, such as a Claude Design or Artifact') and when-not ('live apps built with v0, Lovable, Bolt or Replit are better tested through their published public URL'; temporary preview links expire). It names the follow-on alternatives propose_usability_test and relaunch_usability_test, and clarifies it does not itself start a test.

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