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

No annotations are supplied, so the description carries the full burden. It usefully discloses the validation criteria (MOD-97, length, country support), which is more than a bare 'validate' statement, but it says nothing about what happens on failure, whether a result is a boolean or an error list, or any auth requirements. Partial coverage of a low-risk read operation.

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?

A single front-loaded sentence that leads with the action and immediately lists the three checks. No filler or redundancy.

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, no-output-schema validation tool the description is close to sufficient, but it never states the shape of the result (pass/fail boolean vs. error details), which is the key thing an agent needs to interpret the call. No annotations exist to fill that gap.

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 in the schema, including the 'spaces are ignored' normalization. The description adds no syntax, format, or IBAN example beyond what the schema already provides, so the baseline of 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?

The description names a specific verb (Validate) and resource (IBAN) and enumerates the exact checks performed: MOD-97 checksum, expected length, and country support. The verb inherently separates it from the sibling generate_iban, so an agent can select it without inspecting the 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 verb — validate when you need to check an IBAN — but there is no explicit when/when-not statement and no routing to alternatives such as generate_iban or list_countries. Adequate but leaves the agent to infer the trigger context.

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