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

The annotations already cover the safety profile: this is a non-readOnly, non-destructive, closed-world operation. The description adds the accepted input format ('Accepts pdf') and that a result file is returned. However, it says nothing about whether the empty default password makes the output effectively unprotected, or whether the source file is preserved — meaningful behaviors for an encryption tool.

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, front-loaded sentences with no filler; the encryption action comes first and the I/O contract follows. 'Returns the result file' is slightly vague but useful given there's no output schema.

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 two-parameter nested tool with no output schema, the description is adequate but thin: it never explains what happens when the password option is omitted (schema default is an empty string) or how failures/invalid PDFs are reported. The core call can still be made correctly from the schema alone.

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%, so the file object and the password option are fully documented in the schema. The description's 'with a password' maps to options.password but adds no syntax, minimum length, or default-behavior details beyond the schema. Baseline 3 applies when the schema does the heavy lifting.

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 states a specific verb and resource: 'Encrypt a PDF with a password to open it.' The direction of the operation (encrypt, not decrypt) implicitly separates it from the unlock-pdf sibling, but no sibling is named, so the distinction is left to the agent.

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 guidance on when to use this tool versus unlock-pdf or the other PDF siblings, and no prerequisites or exclusions are stated. The usage is only inferable from the tool's name and the encryption phrase.

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