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

Annotations only declare readOnlyHint and openWorldHint; the description goes well beyond them by disclosing the GLEIF fallback behavior (institution null with a reason), a one-day cache, per-call pricing ($0.002 USDC via x402 on Base/Solana/Arc) and the fact that failed calls are not charged. Cost and failure semantics are exactly the kind of context an agent needs before invoking.

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 paragraph with no filler; the core capability is front-loaded ahead of the fallback and payment details. It is longer than strictly needed, but every clause carries distinct information (validation set, fallback, cache, price).

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 an open-world lookup with a single required param and an output schema, the description covers the remaining burden: fallback behavior when no GLEIF record exists, caching, and the x402 payment model. An agent has everything needed to call it correctly, including the cost implication.

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?

Single parameter with 100% schema description coverage, so the schema already documents the 8/11-character format and gives examples. The description adds no syntax or format detail beyond that, so the baseline 3 applies.

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+resource ('Checks a SWIFT/BIC code') and then enumerates exactly what is validated: format, bank code, country/name, location, test/passive flags, branch, plus LEI/legal name/address from GLEIF. An agent knows precisely what this tool returns without opening any schema.

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 domain (it operates on a BIC you supply), but there is no explicit when/when-not guidance and no routing to related siblings such as lei or iban, which overlap in the entity-identity space. Adequate but with a clear gap.

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