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

Annotations already declare readOnlyHint=true and openWorldHint=false, and the description reinforces this with 'Alleen-lezen' (read-only). It also adds context beyond annotations by specifying that the output includes a breakdown (company base plus extra users) and that amounts are exclusive of VAT. It further notes that no personal data is needed, which is extra behavioral disclosure about input requirements.

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?

The description is two concise sentences with no redundant words. The primary action is front-loaded ('Reken uit wat Taklo per maand kost'), followed by the key output details (breakdown, VAT) and a note on read-only and privacy. Every sentence adds value, and it is appropriately brief for a simple tool.

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 simple calculator with one parameter and no output schema, the description covers all essential information: what it calculates, what the output contains (breakdown and VAT note), and that it is read-only and requires no personal data. The only minor omission is error handling or edge cases, but the schema handles the user range, and no additional context is necessary for an agent to call it correctly.

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?

The schema description covers the single parameter fully (range and base user explanation). The tool description does not add new semantic meaning about the parameter beyond restating that it is a number of users and that the first user is in the base. Since schema coverage is 100%, the baseline of 3 is appropriate; the description does not degrade or enhance the parameter understanding.

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 clearly states the tool's function: calculating the monthly price for a given number of users. It specifies the verb 'Reken uit' (calculate) and the resource 'Taklo', and it distinguishes itself from siblings like plan_terugbelmoment or start_gratis_proefperiode by focusing solely on pricing. The purpose is unambiguous and easily differentiated.

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 explains what the tool does but does not explicitly state when to use it versus alternatives. It does not mention exclusions or alternative tools for pricing scenarios. However, the context is clear: an agent would infer to use this for price queries, but there is no direct guidance on when not to use it or when to prefer a sibling.

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