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

Annotations already declare readOnly, idempotent, non-destructive and open-world, so the safety profile is covered. The description adds genuinely new behavioral facts: it is free, the data is one day stale, the timezone is America/Chicago, and there are no inputs — exactly the context an agent needs to avoid mistaking it for live data.

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?

Three short sentences with the most decision-relevant fact ('Free') front-loaded, followed by what it returns and the key caveat. Nothing is padded or repeated.

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 no-argument sample tool with no output schema, the definition covers cost, freshness, timezone, and data nature. The only remaining gap is that it doesn't characterize the report's contents or size, which matters slightly since the stated goal is format inspection.

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?

Zero parameters, so the baseline is 4. The description also confirms 'No inputs', which matches the empty schema and prevents an agent from hunting for arguments.

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 verb and resource ('Returns a day-old sample of the conditions report') plus the exact time basis (previous calendar day, America/Chicago). It implicitly separates itself from get_current_conditions by declaring 'Not live data', though it does not name that sibling directly.

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 a clear when-to-use rationale ('so you can inspect the report format before paying') and an implicit exclusion ('Not live data' → use the live tool for actual conditions). It stops short of explicitly naming the alternative tool an agent should pick instead.

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