get_user_by_username

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

Annotations already declare readOnlyHint=true and destructiveHint=false, so the '[READ]' tag adds nothing new. The remaining text is a bare REST endpoint path, which conveys no behavioral traits such as error behavior for unknown usernames, auth requirements, or response shape.

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 lines with no filler, and the operation is front-loaded in the first line. The endpoint path on the second line is arguably redundant with the tool name but costs little.

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 single-parameter read tool with read-only annotations, the description is minimally adequate. It says nothing about the returned user object or 404-style behavior, and with no output schema present there is no structured fallback for return-value expectations.

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 carries some burden, but it only restates the parameter name ('by username'). It adds no information about username format, case sensitivity, or URL-encoding expectations that would help an agent construct a valid call.

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 and resource (get user) and the lookup key (username), which implicitly separates it from get_user_by_id, get_user_by_short_uuid, and resolve_user. However, it never names those siblings or explains why username lookup is preferable in any situation, so differentiation is inferred rather than stated.

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 when-to-use guidance, no prerequisites, and no mention of any alternative lookup tool despite several siblings (find_user, resolve_user, get_user_by_id) that an agent could confuse this with. The agent must guess which lookup key applies to its data.

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