Elevation at a point

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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is covered. The description goes well beyond this: it discloses nearest-cell (non-interpolated) sampling and the accuracy caveat on steep slopes, the exact success return shape, the non-error null+note behavior for no coverage, and the structured error case for out-of-range coordinates or fetch failures. This fully specifies the behavioral contract.

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 description is front-loaded with the core purpose and then builds out the data source, sampling semantics, return contract, error contract, and attribution in clearly separated paragraphs. Every paragraph earns its place; the middle sentence about "the same open-data pattern every other tool here uses" is mildly redundant context and could be trimmed, but the overall structure is efficient for the amount of behavioral detail conveyed.

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 two-parameter read tool, the description is complete: purpose, data provenance, resolution, accuracy caveats, success return shape, the non-error null path, the error path, and attribution are all covered. The output schema's existence plus the explicit return-shape documentation means an agent knows exactly what to expect before and after invoking the tool. Nothing needed for correct invocation 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 description coverage is 0%, so the description must compensate. It does partially: "at a point" maps the two required numeric params to a coordinate pair, and "out-of-range coordinate" signals that lat/lon have validity bounds. However, it never states the coordinate format or the actual valid ranges (lat -90..90, lon -180..180), leaving the agent to rely on geographic convention.

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?

The opening sentence states a specific verb and resource: "Ground elevation in meters at a point, from Copernicus GLO-30 (~30 m resolution)." It names the exact data source and measurement, making it easy to distinguish from sibling point-lookup tools like buildings_at, land_use_at, and address_at. The purpose is unambiguous and non-tautological.

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 tool's purpose is specific enough that an agent can infer when to use it (any time elevation at a coordinate is needed), and the coverage/error notes clarify when results will be null or failed. However, it never explicitly names an alternative or states when not to use this tool versus a sibling. The open-data pattern remark references other tools generally but provides no routing guidance.

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