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

Annotations already cover the safety profile (readOnlyHint=true, idempotentHint=true, openWorldHint=false). The description adds one genuine behavioral fact beyond them: the tool also *formats*, not just validates, implying output normalization. It does not say what the formatted result looks like or how invalid input is reported.

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 with zero filler; the verb and resource appear immediately. It is arguably a touch terse given the dual validate/format behavior it advertises.

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?

With no output schema, the description is the only source for return behavior, and 'validate and format' leaves ambiguous what is returned on success versus failure and in what format. For a single-parameter utility this is acceptable but not complete.

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 carries its own example ('e.g. 5402-9681'), so the schema does the documentation work. The description adds no extra parameter meaning, which is the baseline case for a one-param tool.

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 pair ('validate and format') and a specific resource ('a Swedish bankgiro number'), so the agent knows exactly what domain object is being checked. It does not explicitly distinguish itself from the sibling validate_plusgiro, but the resource noun does the differentiation.

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?

There is no explicit when-to-use, when-not-to-use, or mention of the alternative validate_plusgiro, so guidance is only implied by the tool name. For a self-evidently scoped validator that is adequate but not helpful.

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