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

Annotations already declare readOnly/idempotent/non-destructive, so the description adds genuinely new operational facts: a $0.001 USDC x402 charge per successful call on Solana and the equivalent HTTPS GET endpoint. It stops short of describing what a failed validation or an unsupported input returns, which is the remaining gap.

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 dense but well-ordered paragraph: purpose first, then the format coverage list, then detection behavior, then pricing/endpoint. Every clause carries information an agent would otherwise have to guess.

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?

With no output schema, the description never says what a call returns — validity boolean, parsed bank/country/branch fields, or failure shape — and does not say how unsupported or unparseable values are reported. For a paid validation call these are meaningful omissions, though coverage of inputs and cost is otherwise strong.

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 0%, so the description must compensate, and it largely does: the enumerated format list maps directly onto the `type` enum values (aba, bic, clabe, cbu, ca-routing, sort-code, bsb, ifsc) and 'auto-detects the type' explains the `auto` default. The `value` parameter's expected string shape and 40-char limit are left to the 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?

Opens with a specific verb and resource ('Validate bank routing identifiers offline') and then enumerates every supported scheme plus the exact check each performs (ABA 3-7-1 checksum, CLABE checksum/bank/plaza, CBU both check digits). It also explicitly distinguishes itself from the sibling iban_validate by naming the path that handles IBAN.

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?

States the tool works offline, auto-detects the format, and routes IBAN callers to /v1/iban-validate instead — a clear exclusion with an alternative. It does not say when a caller should override auto-detection with an explicit type, but overall context is clear.

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