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

Annotations already declare readOnlyHint, destructiveHint:false and openWorldHint, so the safety profile is covered. The description adds meaningful context beyond that: the data is public, the call costs nothing, and it exposes the underlying REST path and verb. What is missing is any note on result volume, ranking or pagination behavior.

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, front-loaded with the core purpose before the coverage detail, and the trailing endpoint path is compact. Slightly overstuffed relative to a 2-parameter tool, but no sentence is wasted.

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 should hint at what comes back, and it does by listing the fields each entry exposes (contacts, websites, receivable document types). Combined with fully documented parameters and annotation coverage, an agent has enough to call it correctly; only result shape and volume remain unspecified.

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%, so the baseline is 3, but the description genuinely adds searchable-field semantics the schema lacks: it names participant identifiers, countries, contacts, websites and receivable document types, which is richer than the schema's generic 'Name, identifier or other identifying text'. The environment parameter's purpose is only covered by the schema, not the description.

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 ('Search the public Peppol business directory') plus the searchable fields, so the agent knows exactly what this does. It does not, however, distinguish itself from the sibling dochorizon_lookup_peppol_participant, which is a closely related Peppol operation, so it falls short of a 5.

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 by the phrase 'by company name, identifier or other text', which tells the agent what inputs are appropriate. There is no explicit when-to-use statement, no exclusions, and the nearby alternative (lookup_peppol_participant) is never referenced, leaving the agent to infer the routing.

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