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

Annotations only declare readOnly and openWorld, so the description carries the real behavioral load: result order matches input order, 0 on open sea, null where no terrain, and the important ground-vs-structure rule (tunnel returns the mountain above, bridge the valley below). It also discloses that a call counts as one request, which is quota information not present in annotations. It stops short of saying whether the response is a bare array or wrapped, but the per-point semantics are unusually well covered.

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 purpose and scope, then result semantics, then alternatives, then the request cost — a sensible order with no filler sentences. It is dense and slightly repetitive on the [lon, lat] form already given in the schema, but nothing is wasted.

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?

There is no output schema, and the description compensates by explaining exactly what comes back: one height per point, in the same order, with 0 and null sentinels. Combined with the explicit sibling routing, an agent has everything needed to call this 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 already has an example, so the baseline is 3. The description adds genuine meaning by fixing coordinate order as [lon, lat] and stressing that points are separate (not a path), which prevents the most likely misuse.

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 ('heights above sea level in metres for a list of separate points'), the input form ([lon, lat]), the 1,000-point cap, and the shape of the answer. It also explicitly separates itself from route_report, area_report and point_report, so an agent can pick it 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 explicit routing: use route_report with the profile part for a route/track climb (because it follows the road), area_report for a grid over an area, point_report for one place with more detail. Both the when-to-use and the when-to-use-something-else are stated.

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