Get User

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

Annotations already declare readOnlyHint, idempotentHint and openWorldHint, so the safety profile is covered. The description adds no behavioral context of its own — nothing about what happens when the username does not exist or whether the lookup is case-sensitive — but with annotations and an output schema in place this is only a modest gap.

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?

One short sentence, front-loaded with the verb and resource, with zero filler. It is efficient, though its terseness is part of why usage and behavioral guidance are thin.

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 lookup with full schema coverage, rich annotations and an output schema that explains the return shape. Nothing essential for invoking it correctly is missing, though a note on not-found behavior would round it out.

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 the 'without @' format, so the schema carries the semantics. The description only restates that lookup is keyed on username and adds no format or edge-case detail beyond the schema.

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 a Mattermost user's profile') and narrows it with 'by username', which implicitly separates it from the sibling search_users. It stops short of explicitly naming that alternative, so it is clear but not fully differentiated.

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?

'By username' implies an exact-match lookup rather than a fuzzy search, which hints at when to use it over search_users. However, no alternative is named and there is no statement about when this tool is inappropriate or what to do if the exact username is unknown.

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