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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the bar is lower, and the description still adds real substance: it discloses the authentication requirement ('Requires a skanfirmy API key') and, in the absence of an output schema, explains the return shape including the raw status_vat literal and derived vat_active/status_vat_code fields. It does not mention ordering, empty-list behavior, or result size limits, which keeps it short of a 5.

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, front-loaded with the resource and return contents, then field semantics, then the auth prerequisite. The parenthetical about null names is earning its place, though the derived-field sentence is dense enough that it reads more like schema prose than tool guidance.

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 takes on the job of explaining return values and does so thoroughly, including the raw-vs-derived status distinction and the null-name edge case, plus the API key prerequisite. What remains unstated — ordering, pagination, and behavior on an empty watchlist — is modest for a simple parameterless read.

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% for the single optional api_key, so the schema already carries the parameter documentation and the baseline of 3 applies. The description's 'Requires a skanfirmy API key' adds context that the key is mandatory overall, though it slightly blurs the schema's 'optional, if not in the header' nuance rather than clarifying it.

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 states a specific verb and resource ('Return the list of NIPs you monitor') and enumerates the fields returned, so the agent knows this is a retrieval of the monitored-watchlist rather than a one-off lookup. It does not explicitly contrast itself with the lookup siblings (sprawdz_nip, sprawdz_lista_nip), leaving differentiation to inference from 'you monitor'.

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: this is the tool to inspect the set of NIPs currently being observed and their latest VAT status. There is no explicit when-to-use/when-not guidance and no pointer to observe_nip/unobserve_nip for modifying the list or to sprawdz_nip for ad-hoc checks, so the agent must infer the boundary itself.

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