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

Goes well beyond the readOnly/idempotent annotations: it discloses pre-flight control-sum validation of INN/KPP/BIK/accounts and that the document is NOT created on bad requisites, that the returned link expires in 24 hours, and that a working-day payment deadline can be appended via the production calendar. These are consequential behaviors an agent must know before calling.

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?

Front-loads what the tool produces, then validation behavior, then optional features and the return value, with minimal filler. The bilingual tail sentence is slightly redundant with the opening, which keeps it short of a 5.

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?

With no output schema, the description carries the return-value burden and does so: a PDF and/or DOCX link valid 24 hours, plus an optional base64 payload. Validation-failure behavior is covered; error shapes and pagination-equivalent concerns are not described, leaving a small gap for a complex nested-parameter tool.

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; the description still adds meaning by explaining the VAT branch (rate vs. «Без налога (НДС)»), the sum-in-words/signature rendering driven by seller fields, and the working-day payment clause tied to payment_due_working_days. It is more than a restatement of the schema, though it does not clarify every optional field.

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?

States a specific verb and artifact (forms a Russian-form schet na oplatu) and enumerates the document's structure (banking block, seller/buyer, line-item table, total, VAT, sum in words, signatures). This clearly separates it from siblings like make_act or validate_requisites without opening either 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 name and the description of what gets generated, but there is no explicit when-to-use/when-not guidance or routing to alternatives such as validate_requisites (whose job the built-in INN/KPP/BIK check partially overlaps) or amount_in_words. An agent can infer intent, but the decision guidance is left to inference.

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