discord_set_bot_username

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

Goes well beyond the annotations: discloses the rate limit magnitude (~two changes per hour), global blast radius across all servers, name-rejection behavior, and the 429 failure mode requiring a wait. Annotations only say readOnly=false, idempotent=true, openWorld=true, destructive=false; the throttling and rejection semantics are the genuinely useful additions.

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 verb statement followed by the warning, scope, failure mode, exclusions, and return value. Four sentences, no repetition, and the highest-risk information (rate limit, global effect) appears early.

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?

Covers mutation semantics, rate limits, failure handling, scope, sibling exclusions, and even the return value despite an output schema existing. Nothing an agent needs before invoking a single-parameter, high-consequence write is missing.

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% and the single parameter already documents its 2–32 character constraint, so the description adds no parameter-level detail. Baseline 3 is appropriate given the schema does all the work.

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?

Opens with a specific verb+resource and scoped object ('Change the bot's global username'), then explicitly rules out the two most confusable siblings: the server name (discord_set_guild_name) and the bot's nickname (discord_set_bot_nickname). An agent can pick the right tool without opening any schema.

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 strong operational context: it applies in every server, is heavily throttled (~2/hour), may be rejected for taken/reserved names, and fails with 429 when throttled. The exclusions point toward alternatives for nickname/server-name changes, though it never names those sibling tools explicitly.

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