Change a Scaleway IAM User's username (login identity)

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

Annotations already declare the tool as non-readOnly, openWorld, idempotent, and non-destructive. The description adds critical behavioral context: the confirm parameter is a safeguard ('Requires confirm=true') and changing username without proper notification will prevent the user from signing in next time. This disclosure of side effects on user login ability goes beyond the structured annotations. The 'Live-probed on bogus ids only (404 shape)' comment adds transparency about how the tool validates the user_id (by making a live existence check and returning 404 for invalid IDs). No contradictions with annotations.

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?

Three short sentences that are front-loaded and each provide distinct value: first sentence states purpose, second sentence gives critical usage condition and consequence, third sentence adds testing behavior detail. No unnecessary words. Every sentence earns its place.

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 the tool is a simple mutation with 3 required parameters and no output schema, the description covers the main behavioral aspects: purpose, required parameter condition, side effects, and validation behavior. It does not explicitly describe what the API returns (success/error), but since no output schema is provided, this is not a major gap. The description is sufficient for the agent to understand when and how to call the tool and what to communicate to the user.

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 67% (user_id lacks description; new_username and confirm have basic descriptions). The description adds value by explaining why confirm is required (to force user notification) and the consequence of not setting it correctly. The 'new_username' parameter is adequately described in the schema. The description does not add detail for user_id, but UUID format is standard. Overall, the description enriches the meaning of the confirm parameter beyond the schema's 'Must be explicitly true' by linking it to the login impact.

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 title and description clearly state this tool changes the username (login identity) of a Scaleway IAM user. The description explicitly says 'Change what the person types to LOG IN', which is a specific verb+resource combination. It differentiates itself from sibling tools like scaleway_iam_update_user (general update) and scaleway_iam_update_user_password (password change) by focusing uniquely on the username.

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?

The description provides strong usage guidance: 'Requires confirm=true - they must be told, or they cannot sign in next time.' This warns the agent that setting confirm to true is not just a formality but that the user must be informed to avoid lockout. It implies when to avoid using (if user cannot be notified) but does not explicitly name alternative tools or scenarios when not to use it. The guidance is clear and actionable.

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