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

Annotations already declare readOnly/idempotent/openWorld, so the safety profile is covered. The description goes beyond that with a meaningful behavioral trait: the directory is an opt-in business-card index, so it can produce false negatives, and absent results must be confirmed elsewhere. That is real context the annotations cannot express.

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 sentences, each earning its place: purpose, usage linkage, and the false-negative caveat. The most decision-relevant content (what it searches and what it returns) is front-loaded.

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?

No output schema exists, so the description must convey the return value, and it does (a schemeCode:value participant identifier). Combined with the coverage caveat and the named follow-up tool, an agent has everything needed to call it correctly and interpret a null result.

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 q, limit and country are already fully documented in the schema, including format and default. The description only implies free-text matching and country filtering without adding format or syntax beyond the schema. Baseline 3 for schema-carried semantics.

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 (search) against a specific resource (the Peppol Directory) and names the exact output artifact it produces: a "{schemeCode}:{value}" participant identifier. It explicitly differentiates itself from the sibling lookup_participant, so an agent can route between them without opening either schema.

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?

Gives an explicit when-to-use case (turn a company name into a participant identifier), names the downstream tool that consumes the result (lookup_participant), and adds a when-not-to-conclude rule: absence from the directory does not prove a company is off Peppol, so confirm with lookup_participant.

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