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

Annotations already declare readOnly/openWorld/non-destructive, so the bar is lower; the description adds genuinely non-structured facts: US$0.002 per call and 3 free calls a day, plus the returned fields (symbol, confidence, timestamp). It does not say what happens on rate-limit or over-25 exhaustion, keeping it below 5.

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?

A single front-loaded sentence with the usage trigger first, then capability, formats and cost — no filler and no repetition of the schema.

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 an output schema and full annotation coverage, the description supplies everything extra an agent needs: cost, free-tier limit, batch cap, and accepted input syntaxes.

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, but the description goes beyond the schema by naming a third identifier form (price id, e.g. coingecko:bitcoin) that the schema description omits, which materially changes how the agent fills the parameter.

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+resource (live US-dollar crypto prices), the batch limit (up to 25 assets), and the accepted identifier formats. An agent can distinguish it from sibling liquidation_price without opening either schema.

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?

"Use when you need a current crypto price" is an explicit trigger condition, and the batch/format guidance helps scope the call. It stops short of naming alternatives or exclusions (e.g. when to prefer liquidation_price), so not a full 5.

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