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

Annotations already declare readOnly, idempotent, non-destructive, closed-world, so the safety profile is covered. The description adds genuinely useful behavior beyond that: the NIP keying and the null-return semantics when a company has no KNF entry, which an agent needs to interpret an empty result.

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, zero filler. It front-loads the register's identity and scope, then closes with the keying and null behavior an agent needs for result interpretation.

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 usefully names the returned fields (kind, KNF number, status, registration/decision/strike-off dates, services) and the null case. All three parameters are optional and schema-documented, so the definition is nearly complete; only explicit alternative-routing guidance 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 schema already documents krs, nip, and name fully. The description's 'Keyed by NIP' hints at a preferred lookup key but adds no format, precedence, or fallback detail beyond what the schema provides.

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+resource — the KNF register of licences and entries for a financial company — and enumerates the entity types it covers (banks, payment/e-money institutions, insurers, agents). The topic is distinct from every sibling (debt registry, sanctions, court gazette), so an agent can route to it without opening the 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?

The description says the tool is 'Keyed by NIP' and returns null when no KNF entry exists, which implies usage, but it never states when to prefer this over siblings or what prerequisites apply. No exclusions or alternative-routing guidance is given.

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