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), and the description adds substantive behavior on top: two distinct output modes, result caps (15 towns vs 20 places), deduplication at nearest point, that a town's own sights are excluded, that distances are straight-line not road, and that unknown places or empty radii return an error message. This is rich context an agent cannot get from the annotations.

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-loaded with the core purpose and ordering before any detail, and nearly every clause carries information (modes, caps, distance caveat, alternatives, error behavior). It is somewhat dense and semicolon-heavy with minor redundancy on the straight-line distance point, but there is no filler.

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?

Despite an output schema existing, the description still conveys the shape of results, the caps, the dedup rule, and failure behavior — so an agent knows what it will get and what errors mean. For a 5-parameter, dual-mode tool, nothing needed to call it 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%, so the schema already documents every parameter and the baseline would be 3. The description goes modestly beyond it by explaining the semantic consequence of `type` (flat list vs town-grouped day-trip view) and reinforcing the place-or-coordinate mutual exclusivity, though most of this is echoed in the schema descriptions.

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 ('List the places Meridian Dispatch covers near a place or a coordinate') plus ordering ('nearest first') and the two modes of operation. It explicitly names the siblings it is not for ('get_destination has them', 'to search by theme use search_guides'), so an agent can route correctly 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?

Gives concrete use cases ('day trips from a base', 'what else to see near a sight') and names two alternatives with the condition that selects them: get_destination for sights inside one town, search_guides for thematic search. When-to-use and when-not-to-use are both explicit.

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