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

The annotations already mark the tool read-only, idempotent, and open-world, but the description adds meaningful behavioral detail beyond those hints: it reports UNKNOWN until Core has enough eligible archived forecast-versus-instrument pairs, never corrects forecasts, and never predicts regime end. This explains the tool's safety profile and limitations clearly. There is no contradiction with the annotations.

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?

The description is compact: it states the core function, the sentinel behavior, the exclusions, and the decision-support framing in only three sentences. Every sentence adds distinct information, and the most important purpose statement is front-loaded. There is no filler or redundant restatement 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?

For a simple two-parameter read-only tool, the description covers most of what an agent needs: the result concept, the separate dimensions of wind speed and direction, the UNKNOWN sentinel condition, and the main limitations. However, there is no output schema, and the description does not specify the exact return shape, scale, or value type for reliability, which leaves a small gap for an agent trying to interpret the response.

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%, with lat and lng each described by range and meaning. The description only adds 'at a coordinate', which maps directly to the two parameters but does not add new semantic detail such as coordinate format, precision, or handling. With full schema coverage, the baseline of 3 is appropriate.

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 a specific verb ('Return') and a clearly defined resource ('historical forecast reliability at a coordinate'), and further narrows it by stating output is separated for wind speed and direction. This is distinguishable from the sibling tools on its face: check_operability, list_domains, and sense_location all have different implied purposes. The closing 'Decision support' clarifies the intended role without ambiguity.

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 gives useful context for when to rely on the tool ('Decision support') and explicitly states what it is not for: it 'never corrects a forecast or predicts when a regime will end.' This gives the agent guardrails against misuse. However, it does not name any alternative tool for those excluded use cases, so it stops short of full when-to-use-versus-alternative guidance.

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