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

The annotations already declare this as a non-read-only, destructive mutation. The description adds useful behavioral scope: the chosen account becomes what telegram_* tools use when no `account` is provided. However, it does not mention persistence, reset behavior, or any confirmation/effects of overwriting an existing default beyond what the annotations imply.

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?

Two short sentences with no wasted text. The key usage condition is front-loaded, followed by the parameter source, which is exactly what an agent needs.

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?

This is a simple one-parameter configuration tool, an output schema exists, and annotations cover mutation safety. The description supplies the essential context: what the default affects and where to get a valid account identifier.

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 100%, so the schema already defines the single `account` parameter. The description adds practical value by saying to pass the account's label or id and by pointing to telegram_list_accounts as the source for valid identifiers.

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 action and resource: choosing/setting the default Telegram account used by telegram_* tools when no `account` is supplied. It also distinguishes this tool from telegram_list_accounts by referencing that sibling as the place to find valid labels or ids.

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 explains when to use this tool: to choose the default account used by telegram_* tools when no explicit account is given. It also points to telegram_list_accounts for obtaining a valid label or id. It does not state explicit exclusions or what to do if a default already exists.

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