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

Beyond the readOnly/idempotent annotations, the description discloses conditional behavior: it returns a verdict with assumptions and non-modelled caveats, abstains with a neutral table when data is unreliable or venues are tied, and changes behavior in high-regulation jurisdictions by omitting signup links. This significantly enriches the annotations and sets correct expectations.

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 front-loaded with the core purpose, then efficiently lists the verdict contents, abstention triggers, and jurisdiction-specific behavior. Every sentence adds decision-relevant information with no padding.

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 tool with five parameters, rich annotations, and an output schema, the description is complete: it covers purpose, inputs in context, return contents, uncertainty handling, and legal/jurisdiction behavior. An agent has enough guidance to invoke the tool correctly without relying solely on structured fields.

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%, so the schema already documents all five parameters and their meanings. The description adds minimal parameter-level insight beyond requiring a user country and implying a personalized verdict, which matches the baseline rather than exceeding it.

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 opens with a specific verb ('Decide') and a specific resource ('which covered exchange has the lowest effective trading fee for a specific user') and explicitly contrasts itself with 'returning a table.' This clearly distinguishes it from table-returning sibling tools like compare_fees and get_exchange_fees.

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 gives clear usage context: it is for deciding a verdict for a specific user, requires a country, and abstains under defined conditions. It does not explicitly name sibling alternatives, so it stops short of a 5, but the 'instead of returning a table' contrast and abstention criteria provide solid guidance.

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