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

Annotations already declare readOnlyHint, idempotentHint, destructiveHint=false and openWorldHint=false, so the safety profile is covered. The description adds real behavioral value by enumerating the response contents (length_km, exact GeoJSON LineString, center, links.map, ordered places_along) in the absence of an output schema, plus the caveat about not substituting straight-line segments. It omits error/not-found behavior, which keeps it from a 5.

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?

Two sentences, zero filler, with the resource and return fields front-loaded and the mapping caveat placed last as a usage note. Every clause carries information an agent would otherwise have to guess.

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 one-parameter read tool with full schema coverage, the description is close to complete: it compensates for the missing output schema by naming the returned fields and the geometry format. The remaining gap is failure behavior for an invalid or unknown ID, which an agent may need when handling misses.

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 already documents both accepted forms with an example ('7 or 7-wukang-road'). The description restates the same 'by ID or slug' semantics without adding constraints such as slug normalization or case sensitivity, so the baseline of 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 and resource ('Retrieve a curated walking route by ID or slug') and enumerates the returned payload, so it is clearly the single-route fetch rather than a listing. It does not explicitly name list_routes or search_places as the alternatives, so differentiation is implied by 'by ID or slug' rather than stated.

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 only guidance given is about how to consume the result ('Use the LineString geometry rather than straight-line segments when mapping'), which is genuinely useful but is output-usage advice, not tool-selection advice. There is no explicit statement of when to call this versus list_routes or search_places, nor any note about what happens when the ID is unknown.

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