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

Annotations already establish readOnly, idempotent, non-destructive, open-world behavior, so the safety profile is covered. The description earns credit for two things annotations cannot convey: the per-call cost and the geographic coverage limit that determines failure. It does not state what happens when no station is within radius or how results are ordered.

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?

Two sentences, no filler, with the return fields front-loaded and the constraints (cost, coverage) trailing. Every clause carries information an agent would otherwise have to infer.

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?

The output contract is fully covered by the enumerated return fields, and cost/coverage are stated. However, with 5 parameters, zero required fields, and 20% schema coverage, the description leaves a genuine ambiguity unresolved: whether lat/lon or place must be supplied, and how limit/radius_km shape results. That is a meaningful gap for a paid call.

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 only 20% (only `place` is documented), so the description must carry the parameter burden and does not. It never explains lat/lon ranges, the limit cap of 10 stations, or that radius_km (default 100, max 300) defines "nearby"; the word "nearby" and the output field "distance" only loosely imply the radius concept.

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?

Uses a specific verb+resource ("Find nearby USDA NRCS SNOTEL stations") and enumerates exactly what comes back: snow-water equivalent, snow depth, water-year precipitation, temperature, distance, observation date, percent-of-median. No sibling tool covers snowpack, so it is trivially distinguishable from the token/web/geo siblings in the list.

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?

Adds a real usage boundary: "coverage is mountainous western U.S. and Alaska," which tells an agent when not to bother calling, plus a cost signal ($0.01). It stops short of naming alternatives or explaining when to prefer lat/lon over the place parameter, so it falls one step below fully explicit routing guidance.

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