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

readOnlyHint=true already tells the agent this is a safe read, so the description needs to add something beyond that; it only restates the HTTP endpoint. No mention of error behavior (404 on missing id), auth requirements, or response shape — all of which would be genuinely additive here.

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, front-loaded with the action and then the endpoint; nothing is padded. It is efficient, though the endpoint sentence is arguably redundant with the tool name and adds little for an agent.

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 one-parameter read-only getter the essentials are covered by the schema and annotations, but there is no output schema, so the agent receives no signal about what a fetched SSH key record contains or how failures surface. Adequate but with a visible gap.

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% with a single well-documented integer id, so the schema carries the parameter semantics. The phrase "by id" only echoes the schema and adds no format, range, or lookup guidance.

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+scope ("Fetch a single resource by id") and pins the exact upstream endpoint GET /ssh_keys/{id}, which makes the target resource unambiguous when combined with the title. It loses a point because the description body itself never names SSH keys, relying on the title, and the plural tool name (hetzner_get_ssh_keys) sits next to hetzner_list_ssh_keys without an explicit disambiguation.

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?

"Fetch a single resource" implies the by-id case versus listing, but the description never states when to use this instead of hetzner_list_ssh_keys or what happens with an unknown id. No prerequisites, no exclusions, no named alternative.

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