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

Annotations already cover the safety profile (readOnlyHint, idempotentHint, destructiveHint false). The description adds the behavioral nuance that output includes 'honest trade-offs, not just the bigger number', but does not disclose other behavioral aspects like data freshness or rate limits. This is a modest but useful addition, earning a mid-range score.

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 exactly two sentences, both substantive and free of fluff. The primary action is front-loaded, and the second sentence adds practical value about output quality. No wasted words.

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?

Given the presence of an output schema and two optional, well-described parameters, the description covers the essential purpose and output character. It does not discuss prerequisites or edge cases, but for a simple read-only comparison tool it is sufficiently complete.

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 both eu_only and bank_rate_pct having clear default behavior in the schema. The description does not add parameter-specific meaning, so 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 uses a specific verb ('compare'), a clear resource ('low-risk, instant-access crypto savings instruments'), and a well-defined point of comparison ('a typical bank savings account rate'). This distinguishes it from siblings like compare_assets by explicitly scoping the comparison to bank savings accounts.

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 clearly implies the intended use case: when you want to compare crypto savings instruments against a bank savings rate. It provides clear context but does not explicitly name alternatives or state when not to use this tool, so it falls just short of a 5.

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