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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint=false, so the safety profile is fully covered without description help. The description adds useful behavioral detail – that slug yields lowercase hyphenated output and that passport follows МВД 889/ICAO and gost follows GOST 7.79-2000 system B – i.e. deterministic standard-based mapping, but says nothing about handling of non-Cyrillic input or mixed strings.

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-loaded with the core action, then a compact enumeration of the three modes, with no filler. The trailing English one-liner is slightly redundant given the body text, which keeps it from being maximally tight.

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 only two parameters, full schema coverage, and no output schema or nesting, the description supplies everything needed to call the tool correctly, including the default system. Only edge-case behavior (non-Cyrillic characters, numbers passed as text) is left unaddressed.

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, but the description goes beyond the schema's terse 'passport (default), gost or slug' by explaining what each enum value actually implements and confirming the default. That is genuine added meaning for the enum parameter rather than repetition.

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+resource (Cyrillic→Latin transliteration) and then names each of the three output systems with concrete use cases, so the agent knows exactly what the tool produces. None of the sibling tools (decline_name, typograph, amount_in_words) does transliteration, so there is no ambiguity to resolve.

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?

Gives clear selection context for each mode: passport for foreign passports/bank cards, slug for page addresses and filenames. It does not state explicit exclusions or name an alternative tool, but the sibling set has no overlapping capability, so the option-level guidance is the relevant one and it is well covered.

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