update_username

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

Annotations already declare readOnlyHint=false, destructiveHint=false, idempotentHint=true, and openWorldHint=true, so the safety profile is covered. The description adds nothing beyond that: it does not say whether this is a partial patch or a full replace, what happens to omitted fields, or that username_id is required to identify the target.

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?

It is a single short sentence with no filler, which is good, but it is grammatically garbled ("a username's description, from name, or auto-create regex") and mixes an ownership claim with a list of fields in a way that reads ambiguously.

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 mutation tool with four parameters, one required, and no output schema, so the description must carry the burden of explaining update semantics. It fails to say whether omitted optional fields are preserved or cleared, what the UUID identifies, or what the caller gets back — significant gaps for an update operation.

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 75%, so the schema already documents from_name, username_id, and auto_create_regex. The description only loosely echoes those field names and adds no format, syntax, or regex-behavior detail beyond what the schema provides, making 3 the appropriate baseline.

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 ("Update") on a specific resource (a username) and lists the fields affected: description, from name, and auto-create regex. However, "from name" is a garbled rendering of the from_name field, and nothing distinguishes this tool's purpose from siblings like create_username, delete_username, or set_username_option.

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?

There is no guidance on when to use this tool versus alternatives — nothing tells the agent whether to reach for update_username instead of set_username_option, set_username_default_recipient, or delete/create_username. No prerequisites, exclusions, or conditions are stated.

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