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

Annotations already declare readOnlyHint=true and openWorldHint=false, but the description adds useful corroboration: 'pure computation, free' tells the agent there is no network call, no side effect, and no cost, and it discloses the return shape (validity boolean plus country). It does not say whether malformed input yields an error or a false validity result.

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?

Two short sentences, zero filler, with the operation and algorithm front-loaded and the return/cost note second. Every clause carries information.

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 one-parameter, read-only, purely computational tool with full schema coverage and annotations, this is nearly complete. The one remaining gap is behavior on malformed or unsupported-country input, which the agent must discover by calling.

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 schema already supplies an example IBAN and notes that spaces are ignored, so the description adds essentially nothing about the single parameter. Baseline 3 applies when the schema does the heavy lifting.

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 states a specific verb and resource (validate an IBAN) and names the exact algorithm (official mod-97 checksum), plus what it returns: validity and country. It does not explicitly differentiate itself from near-neighbors like bursia_luhn_check or bursia_email_syntax, so it falls 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 resource name — check an IBAN before relying on it — but there is no explicit when-to-use, when-not-to-use, or pointer to an alternative. 'Pure computation, free' hints at a cheap pre-check but never states the workflow condition.

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