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

Annotations already cover the read-only/non-destructive profile, so credit goes to the added context: it discloses a subscription-key auth requirement, an accuracy caveat ("not survey-grade"), and semantics for returned fields (clamped vs raw elevation, bathymetry source). These are meaningful behavioral traits not present in the annotations or schema.

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?

The purpose is front-loaded, followed by output-field semantics and then caveats. It is dense but each sentence carries information; the field-list sentence is slightly terse and would read better as structured output documentation, 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?

With no output schema, the description appropriately explains the return fields, auth requirement, and accuracy limitation, which is nearly complete for a simple 2-parameter sampler. Only the lack of usage context keeps it from being fully complete.

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 description coverage is 100%, with both lat and lon fully documented including bounds, so the schema carries this dimension. The description references lat/lon only in passing and adds no format or usage detail beyond the schema. Baseline 3 is appropriate.

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?

"Sample terrain at lat/lon" gives a specific verb (sample) and resource (terrain) with the required inputs, which is easy to distinguish from sibling tools like route, isochrone, or geo_analyze. However, it never explicitly contrasts itself against any sibling, so an agent must infer the boundary.

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 description states what the tool does but gives no guidance on when to use it versus alternatives, and no exclusions or prerequisites beyond the auth note. The agent gets no routing help.

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