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

Annotations already indicate readOnly=false and destructive=false. The description adds the functional effect of preventing opening or printing, but it does not disclose whether the tool creates a new protected PDF, overwrites the input, or what happens to existing passwords/permissions.

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?

The description is concise and front-loaded, with the core action stated immediately. The opening phrase repeats the tool name and '[category: pdf]' is minor metadata, but there is no meaningful 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?

For a mutating tool with no output schema, the description is thin on outcome: it doesn't state what a successful call returns or whether output is a new file. The schema covers parameters well, so this is adequate but has clear gaps around result and side effects.

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 100%, and the schema already explains file size, password semantics, encryption, and permissions. The description adds no parameter-level meaning, so the schema carries the full burden as expected.

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 action ('Add a password') and resource ('a PDF'), and clarifies the intended effect: preventing unauthorised opening or printing. It does not explicitly contrast with siblings like pdf_unlock, but the protect/unprotect distinction is reasonably inferable.

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 implies when to use the tool (when a PDF needs password protection) but provides no explicit when-not guidance or references to alternative tools such as pdf_unlock. No prerequisites or exclusions are mentioned.

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