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 a solid job: it discloses that whiteout deletes the underlying text from the file, that replace_text with empty text deletes the line, that objects stack in order (last on top), and that API signatures don't count toward the site limit. It omits auth/rate/error context and whether the source file is overwritten, but the critical destructive behaviors are surfaced honestly.

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?

Purpose is front-loaded in one line, then structured per object type; given 0% schema coverage the density is justified. It is long and dense, but nearly every clause carries required information rather than filler.

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 explained, and the object-type reference compensates for the empty schema. What's missing is prerequisite/auth context and any when-to-use-vs-sibling routing, but for a complex 2-parameter tool the description is otherwise sufficient to invoke it correctly.

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 the description fully compensates: it defines file_url, the intent of objects (ordered, last on top), the fractional 0–1 coordinate system anchored top-left, the box format [x0,y0,x1,y1], point-based sizes, and the per-type fields (text wrap, font enums, colors, signature lines/image_url, point lists for line/arrow/ink, baseline for replace_text). This is meaning far beyond the bare array-of-objects schema.

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+resource set ('добавляет на страницы текст, подпись, картинку, закрашивание, пометки и фигуры') and then enumerates the exact object types it can place. This capability set is clearly distinct from the many conversion/utility siblings (watermark_pdf, add_page_numbers, compress_pdf); an agent can identify this as the general-purpose page editor without opening the schema.

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 by the enumeration of capabilities, so an agent can infer 'use this when you need to place objects on pages'. However, it never states when to prefer edit_pdf over the overlapping siblings (sign_pdf for signatures, redact_pdf/watermark_pdf for overlays, replace_text vs a full redaction), leaving the boundary to inference.

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