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

Annotations already declare readOnlyHint=true, confirming this is a safe read operation. The description adds useful context by enumerating exactly which metadata fields are returned and noting the JSON output format, providing specificity beyond the annotation without contradicting it.

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, focused sentence with no filler. The main action and output are front-loaded, and every phrase earns its place by defining scope and return format.

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 simple, read-only, one-parameter tool, the description is complete: it states input requirements through the schema, the operation itself, the specific output fields, and the return format. No output schema exists, but the description compensates by naming what is returned. No critical information is missing.

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?

The schema provides 100% coverage for the single 'pdf' parameter, describing it as a file_id or base64-encoded PDF. The description adds no additional parameter-level detail, so the baseline 3 applies: 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 action ('Read') and a specific resource ('a PDF's metadata (title, author, subject, keywords, creator, producer, dates) plus page count and page size'), and specifies the return format ('as JSON'). This clearly distinguishes pdf_info from text extraction, form reading, and metadata-writing siblings.

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 the tool is for retrieving metadata and page-level information, which provides clear context for when to use it. However, it does not explicitly name alternatives or state when not to use it, so it falls short of a 5.

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