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

With no annotations provided, the description carries the full behavioral burden. It usefully discloses that inputs must be public URLs, that at least two are required, and that input order determines page order. It says nothing about failure behavior (unreachable/encrypted/protected PDFs), size limits, or what happens if merging fails partway.

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?

Two compact sentences with no filler, front-loading the core action followed by the ordering rule and the parameter constraint. Every clause adds 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?

An output schema exists, so return values need not be described. For a simple single-parameter merge tool the description covers the action, ordering behavior, and input constraints. The remaining gap is error/failure handling for bad or inaccessible URLs, which is minor given the tool's simplicity.

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 description coverage is 0%, so the description must compensate for the single undocumented parameter — and it does: file_urls is defined as a list of public PDF URLs with a minimum of 2 entries, and the ordering semantics ('order of files = order of pages') give real meaning the schema cannot convey. It stops short of format details such as whether the array must be non-empty strings or URL scheme restrictions.

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 and resource ('Объединяет несколько PDF в один' — merges several PDFs into one), which is unambiguous and clearly distinct from siblings like split_pdf or extract_pages. It does not explicitly name alternatives, but the operation itself cannot be confused with any sibling.

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?

Usage is implied rather than stated: the agent can infer this is the tool for combining files, and the 'minimum 2 files' note hints at a precondition. However, there is no explicit when-to-use vs. when-not-to-use guidance, no mention of alternatives such as split_pdf, and no prerequisites for the operation.

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