x_api_get_users_by_username

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

With no annotations, the description carries the full burden and does exceptionally well. It discloses read-only risk, required permissions (bearer token, OAuth scopes), environment-selection behavior, common failure conditions, and safety warnings about sensitive data. This goes far beyond a simple read-only hint.

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 well-structured with labeled sections, but it contains redundancy: 'Get User by username' appears in both the opening and 'Use when', and the read-only property is stated twice. While the length is justified by the amount of context, tighter wording would improve it.

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?

Given no annotations and no output schema, the description covers a lot: required permissions, environment behavior, expected response wrapper shape, common failures, and an example call. The inner 'data' object is not detailed (e.g., user fields), but the overall envelope is specified, and the recommendation of prerequisite tools fills additional context.

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 explains the required 'username' parameter and clarifies the roles of scopeTenantId, scopeUserId, scopeAccountId, and credentialKey in environment selection. However, authorizationKey and preferredAuthType are not described, leaving some parameters semantically unexplained.

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 states a specific action: 'Get User by username.' This clearly identifies the resource and operation. However, it doesn't distinguish itself from the similar sibling tools x_api_get_users_by_usernames (plural) or x_api_get_users_by_id, relying on the name alone for differentiation.

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?

Provides explicit 'Do not use when' guidance, noting that exploration should prefer x_schema_discovery or x_query_suggestion, and that auth/configuration tools may be needed first. However, the 'Use when' section merely repeats the tautological purpose, and no explicit comparison is made to sibling user lookup tools, leaving a slight gap.

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