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

The readOnlyHint=true annotation already establishes the safe-read profile, and the description reinforces it with the literal GET endpoint. Beyond that it adds little behavior: nothing about 404/not-found handling, auth requirements, or rate limiting. With annotations covering the safety profile, a 3 is appropriate.

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 scope, then the endpoint. Every clause carries information and there is no 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?

This is a low-complexity single-parameter lookup, but there is no output schema and no annotation detail on returns, so the description is the only place that could mention what comes back (a single firewall object) and what happens on a missing id. As written, the agent knows how to call it but not what to expect back or on failure.

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?

Only one parameter (id) exists and schema description coverage is 100%, so the schema fully documents it as 'The resource's numeric id.' The description's 'by id' adds no syntax, format, or constraint detail beyond the schema, so the 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?

The description states a specific verb ('Fetch') and a retrieval scope ('a single resource by id'), and names the underlying endpoint GET /firewalls/{id}, which pins the actual resource to firewalls. The only weakness is that it calls the entity a generic 'resource' rather than 'firewall', so the reader must lean on the tool name/title and endpoint to resolve what is fetched.

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?

Usage is only implied: 'by id' signals this is for retrieving one known firewall, which implicitly contrasts with the sibling hetzner_list_firewalls. There is no explicit when-to-use statement, no mention of the list alternative, and no prerequisites or error conditions.

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