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

Annotations already declare the safe read-only, idempotent, closed-world profile, so the description need not restate safety. It does add genuine value by disclosing what is returned (bank name, BIC, IBAN id, account type), which matters because there is no output schema, though it says nothing about behavior for unknown or non-Swedish clearing numbers.

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?

One sentence, zero waste, front-loaded with the action and resource and then the payoff. Nothing needs trimming and nothing important is buried.

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 simple one-parameter read-only lookup, the description plus annotations plus the 100%-documented schema cover almost everything. The only remaining gap is error/edge behavior for unmatched clearing numbers, which is minor and partly inferable from the closed-world annotation.

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 parameter is fully documented as 'first 4 digits of the account number'. The description adds the connecting context that this value is a Swedish clearing number, but no format or validity constraints, so baseline 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?

States a specific verb ('Look up') and resource ('Swedish clearing number') and even enumerates the returned fields (bank name, BIC, IBAN id, account type), which an agent can use to distinguish it from the validate_* siblings. It does not explicitly name an alternative such as swedish_account_to_iban, so it stops short of a 5.

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?

Usage is implied by the purpose - call it with a clearing number to get bank metadata - but there is no explicit when-to-use or when-not guidance, nor any routing to related siblings like swedish_account_to_iban or validate_bankgiro.

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