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

Annotations already declare readOnlyHint=true, covering the safety profile. The description adds 'Updates: daily' and the GloFAS data source, but does not disclose limitations or other behavioral caveats. The Gold tier requirement for historical data is in the schema, not the main description. This adds some value but not rich context, so 3.

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. The first sentence front-loads the core action and output details; the second provides use cases and update frequency. Every clause earns its place, and the structure is 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 read-only forecast tool with one optional parameter and no output schema, the description covers purpose, river scope, output fields, use cases, and update frequency. The schema thoroughly documents the parameter, and annotations confirm read-only behavior. No significant information 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 description coverage is 100% for the single 'days' parameter, including the Gold tier behavior, so the schema fully documents the parameter. The description does not add any parameter-specific semantics beyond what is already in the schema, hence the baseline 3.

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 opens with 'Returns a 0-100 river-flood risk forecast' and specifies the exact rivers and output fields (flood_level, rivers_elevated, etc.), giving a clear verb+resource+scope. This distinguishes it from any sibling tool, as none are described as flood-specific.

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 explicitly states 'Call when the user asks about flooding, river levels, or discharge anomalies, or when timing barge logistics, commodity-shipping, or disaster-response decisions.' This provides clear context for when to use the tool, though it does not mention alternatives or exclusions, so a 4 rather than 5.

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