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

No annotations are provided, so the description carries the full burden. It usefully discloses the AES-256 encryption level and the distinction between user and owner passwords, but says nothing about permissions granted/restricted, whether an already-encrypted file is rejected, or what the operation returns/produces.

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?

Front-loaded purpose sentence followed by a tight three-line parameter glossary. No filler, no repetition of structured fields beyond what the 0% schema coverage requires.

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 need not be described. However, for a file-mutating tool with no annotations, the description omits whether the result is a new file/URL or an in-place change, and whether permissions are configurable.

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 0%, so the description must compensate, and it does: all three parameters are annotated (public URL for file_url, open password for user_password, owner password marked optional for owner_password). It does not explain how owner vs. user passwords affect permission restrictions, which is the one remaining gap.

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 and resource ('Защищает PDF паролем') plus the encryption standard (AES-256), which is enough to distinguish it from the sibling 'unlock_pdf' by implication. It does not explicitly name the opposite-operation sibling, so it falls just 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?

There is no statement of when to choose this tool versus e.g. unlock_pdf or sign_pdf, and no prerequisites (e.g. whether the PDF must be unprotected first, or whether an existing password is needed). Usage is only inferable from the name and parameter list.

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