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

With no annotations, the description carries the full behavioral burden; it usefully discloses that both hourly and daily granularity are returned. It says nothing about precedence or fallback when neither 'port' nor lat/lon is supplied (all four parameters are optional), nor about rate limits, error behavior, or units.

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 short sentences, front-loaded with the action and resource, and the second sentence efficiently covers the return shape. No filler or repetition of the tool name.

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 description covers purpose and return granularity, which is reasonable for a read-only lookup with a fully documented schema. It is still incomplete on the ambiguity created by zero required parameters: an agent cannot tell from the text whether port or lat/lon is preferred, nor what the default is if none is provided.

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%, so the schema already documents lat, lon, days (1-7, default 3) and port slug. The description's 'for a port or coordinates' restates the schema without adding format, precedence, or combination rules. 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?

The description gives a specific verb and resource ('Get weather forecast') and enumerates the returned quantities (temperature, wind, precipitation, UV, conditions), so the tool's purpose is unambiguous. It does not, however, distinguish itself from siblings such as get_conditions or get_observations, which plausibly overlap with 'forecast' data.

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?

There is no statement of when to pick this tool over get_conditions, get_observations, get_marine, or get_history. The one implicit routing hint, 'for a port or coordinates', is a parameter hint rather than usage guidance and no exclusions are given.

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