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

Annotations already declare readOnlyHint, idempotentHint, and openWorldHint, so the safety profile is covered. The description adds useful context about which metadata fields are inspected, but 'without changing the file' largely restates the annotations rather than disclosing new behavioral traits such as error behavior or input limitations.

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 a single, front-loaded sentence that packs the tool's purpose, scope, and non-mutating guarantee without wasted words. Every element earns its place.

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 no output schema, the description appropriately lists the returned metadata fields, making the tool's observable result clear. Combined with the fully documented input schema and read-only annotations, an agent has enough information to select and invoke it, though error behavior for invalid or corrupt PDFs is not covered.

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 input schema already fully documents the file parameter and its url/base64/filename options. The description does not add parameter-specific meaning, so the baseline score of 3 is appropriate.

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 uses a specific verb ('Read') with a specific resource ('a PDF') and enumerates the exact metadata returned: page count, title, author, page size, and password-protection status. The phrase 'without changing the file' clearly separates it from the mutating sibling tools like compress_pdf or rotate_pdf.

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 establishes a clear context: use it when you need metadata about a PDF without modifying it. It does not explicitly name alternatives or state when-not-to-use conditions, but the read-only framing and sibling tool names make the appropriate usage inferable.

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