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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description is free to spend its words on payload disclosure, which it does well by naming the data categories that come back. It does not mention pagination or truncation limits for the sources list, 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, front-loaded with the resource and its contents, with no filler. The long parenthetical inventory is dense but each item is a distinct data point rather than padding.

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?

With no output schema, the description carries the burden of explaining return values and does so comprehensively — facts, trailheads with amenity detail, closures, article opening, sources, and URL. Nothing an agent needs to call and interpret this correctly is missing.

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 schema itself documents the slug format and that a page URL or exact name also work. The description only adds provenance ("from search_trails or trails_near"), so the schema is doing the heavy lifting here and 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 (get) and resource (one trail) and enumerates exactly what comes back: facts, trailheads, closures, the About article opening, sources, and page URL. That level of specificity makes it immediately distinguishable from search_trails, trails_near, and list_closures.

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?

"Takes the slug from search_trails or trails_near" tells the agent this is a follow-up detail call and names the two tools that supply its input. It stops short of explicit exclusions, but the routing intent is unambiguous.

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