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

Annotations already declare readOnly, idempotent, non-destructive, and open-world, so the safety profile is covered. The description adds genuinely useful behavioral context beyond that: it names the underlying SML/SMP lookup mechanism, clarifies that registered:false is a normal result rather than an error (a real gotcha for retry logic), and notes the call is free.

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 tightly-packed sentences with the purpose front-loaded, followed by accepted input forms and the key behavioral caveat. Every sentence earns its place with zero redundancy.

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 values need no explanation; the description still adds the important normal-result semantics around registered:false. For a single-parameter, read-only lookup, nothing an agent needs to invoke 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 description coverage is 100%, so the participant parameter's accepted formats are already documented and the description largely mirrors them (full Peppol identifier, bare GLN, German VAT ID, Leitweg-ID). No additional semantics such as normalization or fallback behavior are added beyond the schema.

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: SML/SMP lookup to check whether a partner is reachable in the Peppol network, plus a secondary output (registered document types). This is clearly distinct from sibling check_vat_id, which validates a VAT number rather than network reachability.

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?

Usage is implied — you'd call this to verify a partner before sending a Peppol document — but the description never states when to use this versus the closely related check_vat_id sibling, nor any prerequisites or exclusions. The implied context is clear, but no explicit routing guidance is provided.

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