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

No annotations are provided, so the description carries the full burden of behavioral disclosure. It only explains the parameter format but does not state what the tool returns, whether it saves to file, or any limitations. This is insufficient for a tool that creates new data.

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 concise sentences, front-loaded with the core purpose. There is no unnecessary fluff, and it efficiently conveys the essential information.

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 tool with a single parameter and no output schema, the description covers the main purpose and parameter format. However, it omits what the resulting merged PDF is (returned, saved, etc.) and any potential constraints like size limits. This leaves some gaps for a complete understanding.

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 description adds critical meaning to the 'urls' parameter by specifying comma-separated links in order. Schema coverage is 0%, so this is the only explanation. It clearly defines the format and ordering, which is helpful for correct invocation.

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 clearly states the tool's purpose: merging multiple PDFs by URL into one. This is a specific verb+resource, and it distinguishes itself from siblings like split_pdf or pdf_rotate by focusing on merging.

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 usage is implied: when you need to combine multiple PDFs. However, there is no explicit guidance on when to use this versus alternatives, or any exclusions. For a simple tool, implied usage is adequate but not explicit.

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