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

Annotations already declare readOnly=false and destructive=false. The description adds useful behavioral context that the annotations don't convey: the 24-hour deletion window and the persistence effect of saving. It doesn't clarify idempotency behavior (annotation says non-idempotent) or permissions, but the retention rationale adds real value.

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?

A single front-loaded sentence with no filler; the effect and the reason are both stated economically. Nothing to trim.

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?

An output schema exists so return values needn't be explained, and the annotation profile covers safety. But the description is thin on parameters for a tool whose schema descriptions are empty, leaving an agent to guess what file_id vs file_name semantics are.

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 0% with two parameters (file_id required with pattern ^file_, file_name optional). The description mentions neither parameter nor what they mean, so it fails to compensate for the documentation gap; the pattern and naming must be inferred from the schema alone.

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 ('Keep') and a specific resource ('FynePDF Library'), and distinguishes itself from list_library_files/upload_file by describing the retention effect. Clear what the tool does, though it doesn't explicitly name sibling alternatives.

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 purpose clause implies when to use it (to preserve a result beyond the 24-hour window), giving an implicit trigger condition. However, there's no explicit when-not guidance and no named alternative for those wanting to upload or list rather than persist.

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