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

Beyond the annotations, it discloses an operational cost ('Costs 1 credit per call'), the return behavior ('temporary download link valid 15 minutes'), and the page-size behavior ('auto' vs fixed sizes). These are non-obvious behavioral details that an agent needs and that annotations do not encode.

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 definition is short, front-loaded with the core behavior, and uses line breaks to separate the page-size explanation, credit cost, and return link. The opening phrase repeats the title, so it is not perfectly economical, but no filler remains.

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?

Given the high schema coverage and annotations, the description covers what an agent needs to call it safely: input format/count, page-size options, cost, and download-link expiry. Without an output schema, the explicit return description closes the main gap.

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 100%, so the schema already documents both parameters, including the base64 encoding, image count, and page_size enum values. The description restates the count and page-size behavior but adds little semantic value beyond the schema.

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-resource framing ('Turns 1 to 20 PNG/JPEG images into a PDF') and explicitly states one image per page, which distinguishes it from siblings like merge_pdfs and pdf_to_images. It also covers page sizing, input count, formats, credit cost, and returned artifact.

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 makes the applicable scenario clear: when a user has PNG/JPEG images and wants a PDF with one image per page. It does not explicitly name alternatives or say when not to use it, but the input format and output behavior are unambiguous.

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