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

Annotations already declare readOnly, openWorld, and non-destructive behavior, but the description adds what annotations cannot: an explicit pricing model ($0.01/call via x402 USDC or a card key), the free tier of 25 calls, and the failure policy that failed calls are free. It also makes explicit why idempotentHint is false: repeated calls are charged, and it discloses the 90 m resolution, which implies accuracy limits. This is exactly the extra context the annotations cannot carry.

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 purpose, then use cases, then pricing and safety notes, with every sentence carrying information. The pricing/auth sentence is dense but justified for a paid tool; nothing is 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?

For a two-parameter read tool with no output schema, the description covers what it returns (elevation in metres), the source, resolution, cost, and side-effect profile. The only unaddressed case is behavior at points with no meaningful terrain value, e.g., open ocean or out-of-coverage coordinates.

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 both parameters are fully documented with valid ranges, so the schema already does the heavy lifting. The description only adds a concrete example (lat=59.33, lon=18.07), which confirms decimal formatting but adds no semantics beyond the schema.

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 states a specific verb and resource: it returns ground elevation in metres above sea level for a lat/lon pair. It also names the underlying dataset (Copernicus 90 m DEM via Open-Meteo), which distinguishes it from sibling geo tools such as geo_distance and ip_geolocate without requiring the schema to be opened.

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 concrete scenarios for using it: route planning, flood or terrain risk sizing, and location data enrichment. It does not mention alternatives or exclusions, such as whether it competes with geo_distance or ip_geolocate, but the positive usage context is clear.

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