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

The description reveals core behavior beyond the annotations: merging in the provided order and supporting optional page selection, blank separators, bookmarks, and metadata. Annotations already signal non-destructive behavior (destructiveHint false), so the description does not need to restate that, and it supplies useful context about what the merge does.

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 short and front-loaded with the core action. The opening 'Merge PDFs' heading is slightly redundant with the tool name, but the rest of each sentence earns its place by summarizing scope and capabilities.

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 7-parameter tool with no output schema, the description, combined with a fully documented input schema, is largely complete: it states inputs, minimum count, ordering, and optional behaviors. It does not explicitly describe the output format or delivery, but 'into a single document' is a reasonable characterization and the sibling list makes the PDF domain clear.

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 baseline is 3, but the description adds meaning by stating that input order is preserved and by grouping the optional parameters into feature categories (page selection, separator pages, bookmarks, metadata). This helps an agent understand how the parameters work together even though individual schema descriptions are already present.

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 and resource: 'Combine multiple PDF files (at least 2) into a single document in the order provided.' This clearly distinguishes pdf_merge from related siblings like pdf_split, pdf_reorder, and pdf_interleave by specifying ordered merging into one document.

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 no explicit guidance on when to choose pdf_merge over alternatives. Although it lists capabilities such as page selection, bookmarks, and blank separators, it does not mention exclusions or point to siblings like pdf_interleave for other merge patterns.

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