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

Annotations already declare readOnly, idempotent, non-destructive, open-world, so the safety profile is covered. The description adds genuinely new behavioral context: coverage is limited to NWS forecast points, either an NWS id or USGS site number is accepted, and forecast values are refreshed multiple times daily (freshness/staleness caveat). Error behavior for non-forecast gauges is not stated.

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 sentences, all substantive: identity and return payload first, then input applicability, then freshness. No boilerplate or repetition.

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?

There is no output schema, and the description compensates by enumerating the returned fields including crest, flood category, observations, and flood stages. Combined with the coverage constraint and refresh cadence, an agent has everything needed to select and call it 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% and the single 'site' parameter is fully documented with examples and a pointer to find_river_gauges. The description restates the dual-id acceptance but adds no syntax, format, or validation detail beyond the schema, so baseline 3 applies.

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?

States a specific verb and resource ('current NOAA NWPS river forecast for a gauge') and enumerates exactly what is returned — forecast stage/flow series, crest with flood category, latest observation, flood stages, record crest. That inventory makes it distinguishable from get_river_level and get_river_history without opening their schemas.

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?

Gives a clear applicability condition ('Works for NWS forecast points') and a recency note ('reissued several times a day'), which tells the agent when the data is valid. It does not explicitly contrast with the sibling tools (e.g., use get_river_level for observed current level), so it stops short of full when/when-not routing.

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