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

Goes well beyond the annotations, which already declare readOnly/idempotent/non-destructive/closed-world. It adds that inputs are not stored or logged and, crucially, that a valid result proves only checksum correctness, not real-world existence or ownership — a semantic caveat an agent cannot infer from annotations.

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?

Three short sentences with zero filler; the scope and the 'checksum only' caveat are front-loaded before the privacy note.

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?

An output schema exists, so return-value explanation is unnecessary. For a single-parameter validation tool with full annotation coverage, everything an agent needs to call it correctly and interpret its result is present.

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 baseline is 3; the description still adds meaning by naming the input (VKN / Vergi Kimlik Numarası) and noting it applies to companies, disambiguating it from personal identification numbers. It does not note the schema's maxLength of 64 versus the stated 10 digits, leaving a minor mismatch unexplained.

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?

States a specific verb (validates) and a precisely scoped resource: the check digit of a 10-digit Turkish tax identification number used by companies. The domain scope alone separates it cleanly from validate_iban and validate_national_id without ambiguity.

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 strongly implied by the narrow scope, and the description supplies an important exclusion: this is format/checksum only and does not confirm registration or ownership. It does not explicitly route the agent among its siblings, but their domains are disjoint so routing is self-evident.

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