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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint=false, so the safety profile is covered. The description adds meaningful behavioral context by specifying that it checks format/Luhn/date/age/gender and explicitly warns that it does not prove the person exists, which is important scope information not present in 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?

Two tightly written sentences with zero waste. The core purpose is front-loaded, followed immediately by the key limitation, making the description easy to scan and act on.

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 full schema coverage and clear annotations, the description provides enough context to call it correctly: it names the ID types, lists the checks performed, and warns about the format-only limitation. It does not explain the return shape, but with no output schema and low complexity, this is a minor 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 description coverage is 100% and the single parameter's format is illustrated by the example in the schema. The description adds that the value can be a personnummer or samordningsnummer, but does not provide additional syntax or parsing rules beyond what the schema example already conveys, 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?

The description states a specific verb (Validate) and resource (Swedish personnummer or samordningsnummer), and it lists exactly what aspects are checked (format, Luhn checksum, birth date, age, gender). This distinguishes it from sibling validators like validate_orgnr and validate_iban without needing to inspect their schemas.

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 description implies usage by naming the target ID types, but it does not explicitly say when to choose this tool over sibling validators or provide any exclusions beyond the note that it does not prove existence. The guidance is adequate but leaves the agent to infer routing from the tool name and sibling list.

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