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

Annotations already declare readOnly, idempotent and non-destructive, so the bar is lower; the description still adds real value by spelling out what is checked (length, structure, reserved digit, mod-97), what validity does NOT prove, and that inputs are not stored or logged. That privacy/scope disclosure goes beyond the annotations, though no rate-limit or error-shape info is given.

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?

Front-loaded with the core action and checks, then caveats and privacy note. Efficient, though the returned fields are enumerated somewhat redundantly given an output schema exists.

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 single-parameter read-only validator with an output schema and full annotation coverage, the description supplies everything an agent needs: scope of validation, the meaning of a positive result, and data-handling assurances.

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%, so the single 'iban' parameter and its space/hyphen handling are already documented. The description adds no format examples or normalization details beyond what the schema states, 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?

Specific verb (validates) plus resource (Turkish/TR IBAN) with the standard named (ISO 13616). The 'Turkish (TR) IBAN' scoping distinguishes it cleanly from the national-ID and tax-number siblings.

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 intended use (checking IBAN format/checksum) is implied by the description and the 'format and checksum only' caveat clarifies scope of use. But it never explicitly says when to call this versus validate_national_id or validate_tax_number, nor any preconditions.

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