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

With no annotations, the description carries full burden and does so thoroughly. It details what `valid: true` means (not that account exists or belongs to named beneficiary), warns about currency being country-level, and explains the bank cross-check resolution. It even references response fields like `verification_note` and `currency_note`, providing complete behavioral context.

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 primary purpose, then uses structured paragraphs (validation steps, cross-check, caveats, examples). It is lengthy but every section adds critical information. A slight deduction for verbosity, though the organization and clear headers (CROSS-CHECKS, valid: true, currency) aid readability.

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?

Despite having an output schema, the description goes beyond it to explain response semantics (valid meaning, bank_identifier.resolved_institution, country_currency), potential use cases, and common pitfalls. The provided examples and warnings make the tool self-contained for an agent to use correctly in payment diagnostics.

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?

The schema has a single `iban` string with 0% coverage, so the description must compensate. It provides two clear examples of valid inputs (compact and space-separated) and explains that the IBAN encodes country+bank+account. It doesn't explicitly say 'the iban parameter is the IBAN string', but the examples and context make this unambiguous, adding meaningful semantics beyond the raw schema.

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+resource: 'Validate an IBAN and identify the institution that holds the account.' It clearly distinguishes this tool from siblings by focusing on IBAN validation and bank resolution, and it explains the cross-check feature that is unique to this tool.

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 explicitly states when to use the tool: 'Call this whenever the user supplies an IBAN AND names a beneficiary bank or BIC.' It also provides exclusion guidance, e.g., 'Never rule out the account details on the strength of it when diagnosing a failed payment.' This gives clear context and limits, outperforming typical tool descriptions.

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