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

Annotations already declare readOnlyHint=true, destructiveHint=false and openWorldHint=true, so the safety profile is covered. The description adds value beyond them by stating the operation is non-billing and non-document-processing, and by exposing the underlying GET endpoint. It still says nothing about rate limits, auth prerequisites, or failure modes for unknown participants.

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, and the core purpose is front-loaded ahead of the cost/non-processing caveat. The trailing raw endpoint path is slightly redundant for a tool consumer but compact and occasionally useful for debugging.

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?

With no output schema the description does explain what comes back ('the document types it can receive'), which covers the main gap. For a two-parameter read-only lookup with full schema coverage and annotations, it is nearly complete; only auth expectations and unknown-participant behavior are absent.

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 baseline is 3, but the description contributes an illustrative identifier ('iso6523-actorid-upis::0106:64111512') that conveys the real-world ISO 6523 syntax far better than the schema's terse 'The Peppol participant identifier'. The environment parameter is left entirely to the schema, which handles it adequately via its enum.

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 specific verb and resource ('Look up one Peppol participant by identifier') plus the returned payload ('the document types it can receive'), so an agent knows exactly what the tool produces. The singular 'one ... by identifier' implicitly separates it from the sibling search_peppol_directory, but that alternative is never 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?

'Does not process a document; normally not billed' tells the agent what this is not and roughly what it costs, which is real routing signal. However there is no explicit guidance on when to prefer this over search_peppol_directory, or what the environment choice implies operationally.

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