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

Adds valuable behavior beyond annotations: costs 1 credit per call, returns a temporary download link valid for 15 minutes, and instructs the agent to include the link in the reply. Also explains how page_size affects output. No contradiction with annotations.

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, focused paragraphs: core behavior first, then cost, then output-link handling. The opening sentence slightly repeats the title, but every other sentence earns its place and important information is front-loaded.

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 tool with no output schema, this is complete: input format/count, page-size behavior, credit cost, download-link validity, and the required user-facing instruction are all described. The schema fills in base64 and item limits, so nothing essential 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 coverage is 100%, so baseline is 3. The description adds meaning beyond the schema by explaining that 'auto' makes each page match its image while other page sizes fit the image inside. This extra semantic detail lifts it above baseline.

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?

States a specific verb and resource: 'Turns 1 to 20 PNG/JPEG images into a PDF.' The title adds 'one image per page,' which distinguishes this from related tools like merge_pdfs or pdf_to_images. The core behavior is unmistakable.

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?

Gives clear context: use for 1–20 PNG/JPEG images and optional page_size control. It does not explicitly name alternatives or when-not-to-use, but the constraints and purpose make the appropriate use case clear.

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