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

With no annotations, the description carries the full disclosure burden. It usefully reveals that the output is an advisory recommendation (建議購票期) rather than live pricing data, which tells the agent not to treat results as fare quotes. It says nothing about data freshness, coverage limits, or that peak-season/holiday logic is applied implicitly, so the behavioral picture remains partial.

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?

One compact sentence front-loads the decision to be answered, then the inputs used, then the exclusion clause. Every clause earns its place with no redundant restatement of the tool name.

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 two-parameter, annotation-free, output-schema-free tool, the description covers what it returns (a recommended booking window) and what it is not (real-time fares), and it explains that holidays and peak season are folded into the logic even though they are not parameters. Only the absence of any sibling routing keeps it from being fully complete.

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% (depart = YYYY-MM-DD, dest = 國碼), so the parameters are already documented and the baseline is 3. The description adds that depart is the 出發日 driving the recommendation and that destination factors in, but it does not clarify format expectations or optionality of dest beyond the schema.

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 decision verb and resource: evaluate whether to buy or wait for a Taiwan-departing flight and return a recommended booking window. It also scopes out a capability (不是即時票價 / not real-time fares), which prevents misuse, but it never names a sibling such as ticket_booking_guide to differentiate itself within the toolset.

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?

The decision framing (該買還是該等) implies the usage context of timing a purchase before searching fares, and 不是即時票價 excludes a nearby use case. However, there is no explicit statement of when to choose this over ticket_booking_guide, check_destination_crowd, or plan_leave_2027, so routing 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.