Merge PDFs

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

Given annotations only cover readOnly/destructive/idempotent hints, the description carries substantial behavioral detail: it explicitly states that signatures and AcroForms are dropped, XMP/PDF-A doesn't survive, page boxes and /UserUnit survive, URI links are kept conditionally, encryption is handled with an optional password, and size guards (256 MiB assembly, 50 MiB output). This goes far beyond what annotations alone reveal and precisely informs the agent of post-conditions and failure modes.

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 dense but well-structured: it opens with the core operation, then systematically discloses page-tree destructive effects, encryption handling, and size guards. Every sentence earns its place; no filler or restatement of the tool name. The front-loaded main operation ensures an agent gets the gist quickly, with edge cases and constraints following logically.

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 fairly complex merge tool with nested `encrypt`/`permissions` objects, 7 parameters, and an existing output schema, the description provides all essential decision-relevant context: drop behavior, encryption behavior, output modes, guard limits, and error signals. Nothing an agent needs to safely invoke this tool 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%, and the description reinforces the key parameter semantics beyond the schema: it explains the semantic meaning of `pdfsBase64` (concatenation order), the behavioral consequence on signatures/AcroForms, the conditional behavior of `dropAnnotations`, the assembly guard role of `maxOutputSizeBytes`, and the encryption output implications. This adds real value and clarifies edge cases the schema alone doesn't convey.

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 verb ('Concatenate'), a clear resource ('PDFs'), the input range (2–50), the output type (fresh, self-contained document), and explicitly differentiates behavior from sibling tools by detailing what does and doesn't survive the merge. It is unambiguous and distinctive even among many PDF-related sibling tools.

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 provides explicit contextual behavior and even names the alternative behavior via 'dropAnnotations:true' and the `encrypt` option. It doesn't explicitly say 'use this tool when...' or name a sibling alternative, but the limit and error-code guards make the intended usage clear. The main gap is that it doesn't contrast with split_pdf/extract_pages for page-level operations, but the description sufficiently covers merge-specific use cases.

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