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

With no annotations, the description carries the full behavioral burden and does well: it discloses that server-side extraction happens for PDF/DOCX/txt, that billing is ×3 for PDF/DOCX, the per-text price (€0.001), and that charges go to the Bearer API key. Remaining gaps are operational limits — maximum file size, behavior on malformed URLs, and what happens when both inputs for a side are set.

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 output/behavioral facts are front-loaded in the first sentences and the parameter list is compactly enumerated, so nothing is buried. It is dense to the point of being a run-on paragraph, and a line break or bulleted parameter list would improve scanability without adding words.

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 six-parameter tool with paid, multi-modality inputs, the description covers inputs, defaults, format conversion, multipart restriction and cost model; return-value details are covered by the existing output schema. An agent has enough to call it correctly, with only size limits and conflict-resolution between text/url left implicit.

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% and every property is typed merely as string, so the description is the only source of semantics — and it fully compensates, documenting all six parameters with meaning, defaults and constraints (context 0–10 default 3; ignore_whitespace is a bool that trims lines before comparing, despite the schema declaring it a string). This is meaningful value the schema cannot supply.

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?

Opens with a specific verb+resource combination: unified diff, added/removed lines and similarity percent between two texts or two files. It also names the accepted input modalities (url/upload, PDF/DOCX/plain text), which no sibling tool covers, so an agent can distinguish it from pdf_text, change_monitor or doc_convert without inspecting schemas.

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?

It clearly frames the mutually exclusive input paths — url_a is 'alternative to text_a', url_b 'alternative to text_b' — so the agent knows which parameter combination to pick. It does not, however, state when to prefer this over sibling tools or what happens if both text and url are supplied for the same side, so there are no true exclusions.

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