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

Annotations already establish readOnly, idempotent, non-destructive behavior, so the bar is lower. The description adds genuine extra context: maxTokens truncates the response, and omitting both params returns a topic index. It does not describe the shape of a returned principle, but the safety/behavioral profile is well covered.

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 sentences, front-loaded with what is returned before how to call it. The long topic enumeration is informative rather than padding, though it slightly bloats the first sentence. No wasted clauses.

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 read-only, zero-required-param lookup tool with no output schema, the description covers purpose, modes, topic scope and truncation. The only gap is what a returned principle actually looks like, which matters somewhat given there is no output schema to fall back on.

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 the baseline is 3, but the description goes further by explaining the cross-parameter routing logic (topic = one principle, query = situation search, neither = index) and restates maxTokens' limiting role. That is real meaning beyond the per-field schema text.

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 (Returns) and resource (Better Design's UX principles) and enumerates the covered topics, so the agent knows the content domain precisely. However, it never distinguishes itself from the very similar sibling get-ui-principle (nor get-sales-principle/get-motion-guide), leaving real ambiguity about which of these to pick.

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 a clear situational trigger: 'Use it when the user wants to know how an interface should behave or what its copy should say.' It also explains the three invocation modes (topic / query / nothing). It stops short of naming when NOT to use it versus the sibling principle tools.

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