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

Annotations already cover safety (readOnly, idempotent, non-destructive, closed-world), so the description only needs to add operational detail — and it does: non-bookable ids surface in not_found, and the comparison derives lowest price, shortest duration, best rating gated at 10+ reviews, and free-cancellation flags. It does not mention any rate limits or permission requirements, but none are implied for this read-only tool.

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?

Front-loads the core action and scope, then the derived outputs, then the not_found edge case, then the alternative routing — four tight sentences with no filler despite the long field list.

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 structure need not be repeated; the description still covers the surprising edge case (not_found for non-bookable ids) and the derived-comparison logic. Combined with full schema coverage and rich annotations, 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 the single parameter is fully documented in-schema (pattern ^[0-9]+$, min/max 2-4, tripways.com/t/{id} mapping). The description restates 'by bokun_id' and the 2-to-4 bound without adding new semantics, so the baseline 3 applies.

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 (compare), resource (TripWays tours), scope (2 to 4, keyed by bokun_id) and enumerates exactly which attributes are compared. An agent can distinguish this from get_tour_details or search_tours without opening any 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?

Explicitly routes the adjacent use case away: 'For group totals on a date, use check_availability and get_price_quote.' It also implies the when-to-use case (multi-tour side-by-side comparison) and the 2-4 id bound, leaving little to inference.

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