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

Annotations already declare readOnlyHint=false and destructiveHint=true; the description adds real behavioral context beyond them — re-using an uploadId replaces the stored design (the destructive behavior), the HTML is temporarily hosted by TheySaid, and the mutation does not launch a test. It doesn't cover auth requirements or hosting lifetime, so not a full 5.

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 fallback rationale and the network-block condition are front-loaded, and every sentence carries information (use case, params, overwrite semantics, return shape, negative scope). It is dense but slightly packed, with the return-shape and 'does not start a test' details competing for attention.

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 an output schema present the description needn't spell out return values, yet it summarizes { uploadId, previewUrl, nextStep } and names the follow-up tool, so an agent can chain correctly. Given only two undocumented params and full annotation coverage, the remaining gaps are minor edge cases rather than blocking omissions.

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 description coverage is 0%, so the description must carry the load, and it largely does: uploadId is framed as the hosting key whose reuse overwrites prior content, and html must be the complete, self-contained design HTML. It doesn't detail uploadId provenance or size limits, so it stops short of full compensation.

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 (upload/host) and resource (design snapshot) plus its precise scope: a fallback path used when the PUT to the uploadUrl from prepare_design_snapshot is blocked. It explicitly names the related sibling tools (prepare_design_snapshot, check_design_snapshot), so an agent can distinguish it without opening a schema.

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?

Gives an explicit condition for use ("when the PUT ... is blocked by the environment's network, for example 'Host not in allowlist'"), identifies the primary alternative path, and adds a clear exclusion: "This tool does not start a test." Nothing about when-to-use is left to inference.

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