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

Goes well past the readOnly/idempotent annotations: it discloses that rows beyond the first day are sampled every 2-3h, that hourly_coverage exposes first_time/last_time/sample_interval_hours/truncated, that timestamps are UTC, and that out-of-window hours should be refused rather than substituted. This is the kind of behavior an agent could not learn from the schema alone.

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?

Front-loaded with the payload summary, then escalating operational rules, ending with examples. Fairly long at roughly 180 words, and the coverage/truncation guidance repeats the same idea across two sentences, but nearly every clause is actionable rather than filler.

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 9-parameter, fully-annotated, output-schema-backed read tool, nothing an agent needs is missing: coverage semantics, sampling caveats, timezone handling, and call-shaping advice are all present, and return-value shape is left to the output schema.

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 baseline is 3; the description adds real meaning on top by explaining that hours_from/hours_to returns a dense hour-by-hour window even where the full range would be sampled, and by showing worked examples for both location and lat/lon invocation styles.

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?

Opens with a specific verb+resource+field list: "Blended hourly forecast: temperature, feels-like, humidity, wind, precipitation..." and clarifies row zero semantics ("hourly[0] is the current or next hour"). The hourly granularity and 'blended' framing distinguish it from sibling daily/current tools like get_forecast and get_current_conditions.

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 concrete when-to-use rules: batch days up front ("one call with days: 4 beats four calls"), and use hours_from/hours_to for a contiguous stretch. It does not explicitly name sibling tools such as get_forecast or get_current_conditions, so the agent must infer the boundary itself.

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