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

Annotations only carry readOnlyHint=true, so the description usefully adds that the endpoint is public and requires no API key — a real operational fact an agent needs. It does not cover rate limits or the shape of the response, keeping 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 tight clauses: what it returns, why you'd want it, and the parameter choice — all front-loaded with zero filler. The endpoint mapping is compact supporting detail, not padding.

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?

For a single optional-enum read tool with no output schema and no nested objects, the description covers purpose, auth requirements, use case, and parameter selection. Nothing needed to invoke it correctly 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 coverage is 100% including the enum and default, so the baseline is 3. The description adds value by mapping each choice to a distinct upstream endpoint (/api/nodes/ips, /ipv4, /ipv6), clarifying that family changes the resource fetched rather than just filtering.

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 and resource ('List updown.io's server IP addresses') with the concrete entity being returned, plus the upstream API route. This is clearly distinguishable from sibling list tools like updown_list_nodes or updown_list_checks.

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 a concrete motivating scenario ('to allowlist the monitors in a firewall') and tells the agent how to select the family argument. It does not name an alternative tool or an explicit when-not-to-use condition, but no sibling overlaps enough to require one.

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