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

Annotations already declare readOnly, idempotent, non-destructive and closed-world, so the safety profile is covered. The description adds useful context beyond that: the data source (Peppol Directory / OpenPeppol AISBL) and that each count carries the change since the previous day, which shapes how the agent should interpret results.

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 sentences, no filler, with what is measured and the change metric front-loaded before the parameter note. Every clause earns its place.

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 shape need not be described; the description covers what is counted, the source, the daily-delta semantic, and the full parameter behavior. Nothing needed to call this correctly is missing.

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 0% and the param has only a null default, so the description carries the full burden — and it does: accepted values are a two-letter country code or 'all', and omission means all countries. That is exactly the semantics the schema lacks.

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 gives a precise verb+resource: counts of businesses listed in the Peppol network directory, broken down per country with day-over-day change. An agent can tell this apart from lookup/provider siblings by the 'counts per country' framing, though no sibling is named explicitly.

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?

It states that country is a two-letter code or 'all', and that omitting it returns every country, which is the only branching decision this tool has. It does not name alternatives or when-not-to-use, but for a single-purpose read tool the guidance is sufficient.

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