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

Annotations already declare read-only, idempotent, non-destructive, non-open-world behavior, so 'Read-only; it cannot change a plan' is largely redundant. However, the description adds genuine non-obvious context: the dayCount/stopCount semantics change before 2026-09-28, what stopCount counts (anchors plus backups), and that planUrl opens a prefilled planner.

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 usage trigger is front-loaded and each clause carries information, but the single dense sentence packs return-field details and a historical caveat into one block, making it heavier to scan than ideal. Nothing is padding, yet it could be split for readability.

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?

An output schema exists, so return values needn't be explained, yet the description still summarizes the key response fields and the planUrl behavior helpfully. Combined with the usage trigger and slug sourcing, an agent has everything needed to invoke it correctly.

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%, and both parameters already document accepted forms and example values ('Paris' or 'paris-france'; '3-day-weekend-for-couples'). The description only reinforces that lookup is by slug without adding format or validation detail beyond the schema, so the baseline of 3 is appropriate.

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 with scope: retrieve the full plan for one public itinerary keyed by slug. It enumerates what the plan contains (day-by-day or themed stops, venues, map links, rainy-day and where-to-eat sections, best season), which clearly separates it from list_itineraries and search_itineraries that return collections.

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 opens with an explicit trigger ('Use this when someone wants the full plan for one public itinerary, by its slug'), and the slug parameter points to list_itineraries or search_itineraries as the source of valid slugs. It never states when NOT to use it or names a true alternative for other needs, so it falls short of a 5.

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