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

Annotations already provide readOnlyHint, openWorldHint, idempotentHint, and destructiveHint, so the safety profile is covered. The description adds valuable behavioral context: it returns 'elevation in meters or feet, the source raster resolution, and optionally the DEM acquisition date', mentions 'no auth required', and notes the coverage limit. This goes beyond annotations by describing what the response contains and access requirements. No contradiction with 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?

The description is three sentences, front-loaded with the core purpose, then returns and coverage. Every sentence earns its place: the first states the action, the second lists outputs, the third gives geographic scope and data source. No filler or redundancy. This is highly efficient and easy to scan.

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 simple single-point elevation query with an output schema present, the description covers the essential aspects: purpose, outputs, geographic coverage, data source, and auth. It doesn't mention potential error behavior (e.g., null for ocean coordinates) or precision caveats, but given the tool's simplicity and the output schema handling return structure, this is nearly complete. A small gap on error handling prevents a 5, but it's adequate for an agent to call 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 description coverage is 100%—all four parameters (latitude, longitude, units, include_date) have detailed descriptions including ranges and enums. The tool description adds little beyond this: it mentions that elevation can be in meters or feet and that acquisition date is optional, which aligns with the units and include_date parameters but doesn't introduce new meaning. Since the schema already fully documents parameters, the description provides marginal added value, so a 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?

The description clearly states the tool's function: 'Get ground surface elevation for a single latitude/longitude coordinate from the USGS 3D Elevation Program (3DEP)'. It names a specific resource (ground surface elevation), verb (get), and source, and distinguishes from siblings like gebco (ocean) and opentopo (global) by specifying 'Continental US + territories only'. This is precise and unambiguous.

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 gives a clear context: 'Continental US + territories only (no ocean or international coverage)', which tells when to use it (US land areas) and excludes ocean/international cases. It does not explicitly name alternatives like opentopo.elevation.point or gebco.elevation.point, but the scope is well-defined. The 'no auth required' note also informs setup. This is clear context without exclusions or alternative names, so a 4 is appropriate.

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