update_username

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

The description adds meaningful behavioral context beyond the annotations, specifically that an empty string removes the username. This clarifies a potentially destructive action, which is not covered by the readOnlyHint/destructiveHint annotations. It does not contradict any annotation.

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?

The description is a single efficient sentence that front-loads the action and includes the key edge case. Every word adds value, with no redundancy or irrelevant detail.

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 simple one-parameter mutation tool with an output schema and annotations, the description is complete. It covers the core action and the special removal behavior, which is sufficient for the tool's complexity.

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%, so the description must compensate. It fully explains the only parameter (username) by indicating that it accepts a new username and that an empty string removes it. This provides essential meaning the schema alone lacks.

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 uses a specific verb ('Сменить' = change) and clearly identifies the resource (the account's @username). It also adds the distinct behavior of removing the username via an empty string, which distinguishes it from broader profile tools like update_profile. This fully clarifies the tool's function.

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?

The description implies the tool is for changing or removing the account username, but it does not explicitly mention when to use it over alternatives like update_profile, nor does it state exclusions. The empty-string note is a useful behavioral hint but does not constitute guidance on tool selection.

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