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

With readOnlyHint=true and idempotentHint=true annotations already establishing a safe read profile, the description adds meaningful context: the data source (SnowSure's fleet table), the 30-year window, and the tier semantics (A prime / B favored / C ENSO-proof / D late bloomer / E timing play). No annotation contradiction.

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?

Three tight sentences: first states the result, second details filters, third gives usage examples. Every clause adds value, with no fluff.

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 read-only filter tool with 0 required params, a present output schema, strong annotations, and 100% schema coverage, the description fully complements the available context. Nothing material 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 coverage is 100% with tier, limit, and region all documented, so the baseline is 3. The description reinforces region values and explains tier letters, but adds little beyond the schema's own descriptions.

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?

"Ranked El Niño ski resorts from SnowSure's 30-year fleet table" uses a specific verb+resource pair followed by the exact filter dimensions (region, tier). This clearly distinguishes it from siblings like get_elnino_signal or get_regional_summary.

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 'Use for' clause gives concrete example queries ('best El Niño resorts in Europe', 'is El Niño good for the Alps'), making when to use the tool very clear. It lacks explicit when-not-to-use guidance or named alternatives, but the usage context is unambiguous.

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