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

Annotations already declare readOnlyHint=true and openWorldHint=false, but the description adds substantive context beyond them: 'Mandate never submits applications' and 'Free', which tell the agent this is a pure advisory lookup with no side effects or cost. It stops short of covering result size, pagination, or how stale the regulatory data may be.

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 tight sentences: purpose and scope first, then a compact enumeration of what is returned per obligation, then the information-only disclaimer. No filler and nothing important is buried.

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?

There is no output schema, so the description carries the return-value burden and does so explicitly ('what is needed, which authority, official URL and published contact with source'). Combined with annotations covering the safety profile and a fully documented single parameter, an agent has everything needed to call this 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?

With one parameter at 100% schema description coverage, the schema already explains the country code and the omit-for-EU-wide behavior. The description only reinforces scope ('any of the 27 EU states') without adding format or fallback guidance, so 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?

States a specific verb+resource ('get_post_formation' → what a new company needs after formation), scopes it to the 27 EU states, and enumerates the concrete obligations covered (VAT, EORI, UBO, tax/social security). An agent can distinguish this from get_formation_guide purely on formation-vs-post-formation framing without opening a schema.

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 phrase 'after formation' implies the trigger condition and the schema note says to omit country for the EU-wide part, but the description never names an alternative sibling (get_formation_guide, get_company, find_law) or states when-not to call this. Usage is implied rather than instructed.

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