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

Annotations already declare readOnlyHint, idempotentHint and non-destructive behavior, so the safety profile is covered. The description adds one genuinely useful behavioral fact — that OCR-derived text is flagged as such and SIE is a possible output — but says nothing about failures (missing Id, unsupported file type) or size limits.

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?

Three short sentences, front-loaded with what the tool returns and followed by supported formats and the API reference. No filler; only the bare docs URL is marginal.

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 an output schema present, the description need not explain return structure, and it sensibly focuses on content formats. The remaining gap — no routing against download_inbox_file/get_inbox — is minor but real for a single-param read tool in a 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?

Schema coverage is 100%, so baseline is 3. The description's API path line implies Id is the inbox entry identifier from GET /3/inbox/{Id}, which actually counteracts the schema's misleading 'identifies the folder' wording, but it never states this explicitly as parameter 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?

States a specific verb+resource: returns the readable text content of a single Fortnox inbox file, with the concrete formats it can yield (PDF text, OCR, SIE). It is distinguishable from download_inbox_file only by inference from 'Returns the text for you to read', not by naming the sibling.

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 implied (you have an inbox file Id and want its contents) but there is no explicit when-to-use/when-not guidance. It never says to prefer download_inbox_file for binary/attachment retrieval or read_archive_file for archive entries, both of which are adjacent siblings.

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