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

The readOnlyHint annotation already declares this is a safe read operation. The description adds the concrete REST endpoint mapping, which is useful context, but it does not disclose error behavior (e.g., what happens if the id does not exist) or return characteristics beyond the implicit GET semantics.

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 core purpose and immediately followed by the API mapping. There is no filler, and both sentences carry useful information.

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 operation with full schema coverage and a readOnlyHint annotation, the description covers purpose and endpoint adequately. However, with no output schema, it does not describe the return value or error cases, which is a clear gap for an agent that needs to know what to expect back.

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?

The schema documents the sole parameter fully ('The resource's numeric id.') with type and range, so coverage is 100%. The description adds no additional parameter meaning beyond what the schema already provides, making the baseline of 3 appropriate.

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 ('Fetch') and identifies the endpoint ('GET /firewalls/{id}'), which clearly distinguishes a single-resource fetch from the list_* siblings. However, it does not explicitly name the alternative (hetzner_list_firewalls), and the description itself says 'a single resource' rather than 'a firewall' — the endpoint supplies that detail.

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 gives no when-to-use guidance, prerequisites, or alternative tools. 'By id' indicates a required input, not a usage condition; an agent is left to infer that this tool is for when it already has a numeric firewall id.

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