pdf_info

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

Annotations already declare readOnlyHint=true, openWorldHint=true, and idempotentHint=true, so the safety and remote-access profile is covered. The description adds the accepted input forms (path, base64 data, https URL) and the metadata returned, but it does not add deeper behavioral context such as error behavior, authentication needs, or rate limits. A 3 is appropriate given the annotation coverage.

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 two tightly written sentences with zero waste. It is front-loaded with the core purpose and then the field list, followed by the supported input forms, making it easy for an agent to scan.

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 metadata tool with full schema coverage and no output schema, the description is complete enough: it names the extracted metadata fields and the three supported input forms. Annotations cover the safety profile, and no critical calling detail 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?

Schema description coverage is 100%, so the input schema already fully documents path, data, and url, including the 8 MiB limit and the 'exactly one' constraint. The description reinforces that the PDF can be a root-folder path, base64 data, or https URL, but it does not add syntax or format details beyond what the schema provides. Baseline 3 is correct 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 uses a specific verb and resource: 'Describe a PDF,' and immediately enumerates the metadata fields returned. This clearly distinguishes it from sibling tools like pdf_text, pdf_render_page, and pdf_search, which imply content extraction, rendering, and searching rather than metadata inspection.

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 gives clear context for when to use the tool: to obtain PDF metadata such as page count, title, author, dates, encryption status, and file size. It does not explicitly name alternatives or state when not to use it, so it falls short of the top score, but the intended use case is unambiguous.

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