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

With no annotations provided, the description carries the full burden and does so well: it lists the exact checks performed (document shape, catalog pin, catalog validation, mutation reducer), describes the export gate, and states side-effect guarantees ('Nothing is written, no revision moves and nobody watching the design is notified') plus the `valid` semantics. This is rich behavioral disclosure beyond what any structured field supplies.

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 definition is front-loaded with the three modes before descending into mechanism, and nearly every clause carries information. It is dense but slightly overpacked — the inline return-shape literal and the schema resource URIs could be trimmed given an output schema already exists — so it is not maximally economical.

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 complex, multi-mode validation tool with nested objects, the description covers side effects, the check pipeline, the returned shape, and where the input shapes are published as resources. With an output schema and 100% parameter coverage already present, 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?

Schema description coverage is 100%, so the baseline is 3, but the description adds meaningful framing by explaining how the parameters relate — `operations` are checked against `designId`'s current document 'as ui_builder_apply takes them,' and `baseRevision` is tied to the operations. That relational context is not fully captured by the individual schema entries.

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 states a specific verb and resource ('Check a design without saving it') and enumerates the three input modes it accepts: a whole `document`, a stored `designId`, or `operations` against a stored design. It clearly separates itself from `ui_builder_apply` by emphasizing nothing is written, though it never explicitly distinguishes itself from the sibling `ui_builder_check_design`, which an agent could easily confuse it with.

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 gives clear context for use — validating operations 'exactly as ui_builder_apply would apply them' before committing — which implies the dry-run use case and names the relevant alternative. However, it offers no explicit 'when not to use' guidance and does not route the agent away from `ui_builder_check_design` or `ui_builder_get_design`.

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