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

Annotations already declare read-only, idempotent, non-destructive, closed-world behavior. The description adds the underlying Fortnox GET endpoint and docs URL, which is modest context, but it gives no operational behavior such as error cases, auth needs, or whether it returns file content versus metadata.

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 with the purpose front-loaded before the API endpoint. The docs URL is compact and no sentence is redundant.

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?

With a documented single parameter and an output schema, return-value details are less critical, but the description omits selection context among many inbox/file siblings and does not resolve what the Id points to. That gap matters in this large sibling set.

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 single required parameter has 100% schema description coverage, so the baseline is 3. The description only mirrors the {Id} path token and does not clarify the schema's confusing 'identifies the folder' wording or explain how to obtain the Id.

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 names a specific verb ('Retrieve') and resource ('a single file'), and the endpoint /3/inbox/{Id} confirms lookup-by-ID. It does not distinguish this from similar siblings such as read_inbox_file or download_inbox_file, so it stops short of a 5.

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?

No sentence states when to use get_inbox rather than list_inboxes, list_unprocessed_inbox, read_inbox_file, or download_inbox_file. The agent must infer usage from the name and endpoint alone.

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