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

Annotations already declare readOnly/idempotent/non-destructive behavior, and the description adds a concrete behavioral constraint: inland coordinates 'return an error,' which is exactly the edge-case disclosure an agent needs. It also specifies hourly granularity and the wave/swell output components.

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 contain all the core information — content, audience, and constraint — with no redundancy. Every phrase earns its place, and the description is compact enough to parse quickly.

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?

Given the annotations cover safety and the schema covers most parameters, the description adds the missing behavioral and use-case context. No output schema exists, but the description lists the returned components (wave height, period, direction, wind-wave/swell), so an agent can gauge the result without needing a full response shape.

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?

The description reinforces the lat/lon/zip constraint ('Coastal/open-water coordinates only') and implies the hours parameter via 'hourly forecast.' However, with 60% schema coverage, it does not compensate for the undocumented hours and units semantics, leaving the agent to infer those from defaults and the units enum.

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 resource ('Coastal/marine hourly forecast') and distinctive content ('wave height, period, and direction, plus wind-wave and swell components'), clearly setting it apart from generic weather_forecast/weather_hourly siblings. The 'Coastal/open-water coordinates only' qualifier further narrows the tool's identity.

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?

Explicitly lists intended audiences and use cases ('shipping, fishing, surfing, and coastal-event planning') and warns about invalid input ('inland points return an error'). It gives clear context but stops short of naming alternative weather tools or stating when NOT to use the marine forecast.

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