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

Annotations only declare readOnlyHint=true, so the description usefully adds that rules are returned in evaluation order and what each rule's fields mean (position, direction, action, family, protocol, address/port ranges, comment), plus the non-obvious fact that enablement state is not in this payload. It does not mention pagination or result-size behavior, so it is not fully transparent.

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 tight sentences, front-loaded with the primary content and ending with the API endpoint mapping. The parenthetical field list is dense but earns its place since no output schema exists.

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 carries the return-value burden and does so by enumerating the fields and their ordering, plus flagging the separate firewall-enabled lookup. Nothing critical is missing for a single-parameter read tool, though pagination/limits are unaddressed.

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?

There is a single required parameter (server_uuid) with 100% schema description coverage, so the schema already documents it and the baseline is 3. The description adds nothing about the UUID format or where to obtain it, but nothing is missing either.

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?

Names the specific resource (firewall rules of one server) and enumerates the returned fields in evaluation order. It also distinguishes itself from upcloud_get_server by explaining that the enabled/disabled flag lives there, but the verb itself ('list') comes only from the title and no other sibling is contrasted.

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 implies when to use it (to inspect a server's firewall rules) and provides one useful routing hint—check the `firewall` field of upcloud_get_server to know if the firewall is even active. However, there is no explicit statement of when to prefer this tool, no exclusions, and no prerequisites (e.g., that server_uuid must reference an existing server).

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