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

Annotations only say readOnly/openWorld/idempotent, so the description carries the interesting burden and does it well: it discloses the metered call cost, the OAuth account prerequisite, that the lookup is live rather than cached, and what the result contains. It stops short of covering failure cases (ID not found, no Peppol capability) or latency, so not a 5.

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?

One dense sentence opens with the core question, then layers accepted inputs, lookup behavior, and output, followed by two short sentences on cost and auth. Front-loaded and waste-free, though the first sentence is long enough to be harder to scan than it needs to be.

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, yet the description says what comes back (supported document types and which ID to send to), and it covers the two invocation blockers an agent cannot infer: the metered cost and the OAuth account requirement. Nothing needed to call it 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 100% and already documents both parameters, so the baseline is 3. The description adds value by listing identifier families the schema does not mention (GLN, KvK, SIREN/SIRET) and by explaining that ambiguous numbers are resolved by testing every relevant scheme, which motivates the optional country hint.

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 and resource (check whether a company can receive Peppol e-invoices) and describes the mechanism (querying live Peppol SML/SMP across every relevant scheme). However, it never distinguishes itself from the near-identical sibling 'check_peppol_receivability' or from 'check_belgian_peppol_list', leaving an agent to guess which of the three to call.

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 enumeration of accepted identifier types (VAT, KBO/BCE, KvK, SIREN/SIRET, GLN, Peppol ID) and the note that it checks all relevant schemes imply this is the general-purpose lookup, while the sibling names suggest narrower alternatives. But there is no explicit when-to-use or when-not-to-use statement, and no naming of an alternative tool.

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