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

With no annotations, the description carries the burden and does disclose key traits: the client must exist in the database, an unlinked messenger returns a bot link, and the code is deliberately not returned in the response. It omits rate limits and delivery-failure handling, so not a 5.

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?

Four short sentences, each adding information (scope, channel, prerequisite, response behavior), with the core purpose front-loaded. No filler, though it could be tightened slightly.

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 2-param tool with no annotations and no output schema, the description covers prerequisites and return behavior (no code in response, bot link when unlinked) well. Minor gaps around failure modes remain, but the essentials are present.

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% and both parameters are documented there. The description repeats the channel enumeration (sms, telegram, max) and adds only the indirect 'client must be in the database' constraint for phone, so baseline 3 is correct.

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 ('Отправить код входа') and scopes it to a client-initiated login request, which meaningfully separates it from confirm_login. It doesn't explicitly name the sibling it contrasts with, so it stops short of a 5.

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?

Implicit usage guidance is present ('клиент сам попросил войти' plus the prerequisite 'должен быть в базе'), but there are no explicit when-not conditions or named alternatives like confirm_login, which an agent would need to pick between them.

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