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

readOnlyHint=true already tells the agent this is a safe, non-mutating read, so the description only needs to add value beyond that. It contributes the API route mapping, which aids traceability, but says nothing about rate limits, result density, or how 'step' affects the returned sample count.

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 short sentences, no filler, with the functional scope front-loaded and the endpoint reference as a secondary clause. Every element earns its place.

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?

There is no output schema, so the description carries the burden of telling the agent what comes back — yet it never describes the shape of the time series (samples, timestamps, units) or the effect of 'step' on granularity. For a data-returning metrics tool this is a real gap, though the read-only annotation covers the safety side.

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 all five parameters (including the cpu/disk/network enum and step resolution) are already documented. The description's 'CPU, disk or network' and 'over a window' merely restate the enum and the start/end pair, adding no format or constraint detail beyond the schema. Baseline 3 applies.

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 precise verb ('Fetch') plus the exact resource ('CPU, disk or network time series for one server over a window'), which is enough to distinguish it from hetzner_get_server and every list/get sibling. The added endpoint mapping (GET /servers/{id}/metrics) reinforces the scope. Nothing about the purpose is left ambiguous.

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 phrase 'for one server over a window' implies the scenario (per-server time-series queries) but never states when to prefer this over hetzner_get_server for a point-in-time snapshot, nor any exclusions. Usage is inferable rather than spelled out.

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