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

Annotations already declare readOnly, idempotent, and closed-world, so safety is covered. The description adds genuinely new operational context beyond them: one-day data delay, the free/paid boundary, asset restriction, and a per-IP rate limit of 60 calls/hour. It does not describe how the returned sample is truncated relative to the paid payload, which is the remaining gap.

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 tight sentences, front-loaded with what the tool returns, then the delay/paywall constraint, then the rate limit. Nothing repeats the title or is disposable.

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 one-parameter read-only tool with no output schema, the description covers the essential decision inputs: free-tier limits, one-day staleness, asset restriction, and paywall boundary. An agent can decide correctly whether this tool suffices or a paid sibling is needed.

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% and the single 'asset' parameter already documents that only BTC and ETH are valid. The description restates that restriction without adding format or validation detail beyond the schema, so 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?

States a specific verb and resource: fetch a free sample of the last completed daily trend and regime for BTC or ETH. It explicitly bounds scope against the paid alternatives ('today's live data and the other assets are paid'), so an agent can distinguish it from get_trend/get_regime without opening schemas.

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?

Clear when-to-use context: the free/delayed tier for BTC and ETH only, with live data and other assets requiring payment. It stops short of naming the paid sibling tools an agent should switch to when the sample is insufficient.

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