Add a user to a group

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

Annotations only provide idempotentHint=false, so the description carries the behavioral disclosure burden. It adds meaningful traits: the operation is additive, not a replacement, and requires a confirmation token because group membership grants access. This goes well beyond the annotation, though it does not describe exact response behavior.

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 sentences with every clause earning its place. The additive nature, the alternative, and the confirmation requirement are all stated without redundancy. The most important differentiator is front-loaded.

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 three-parameter tool with no output schema, the description covers the core action, the rationale for confirmation, and the relationship to update_user. It does not describe the return value or what happens if confirm_token is omitted, but the schema already covers the token mechanics, leaving only minor gaps.

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%, so the input schema already fully documents user_id, group_id, and confirm_token. The description reinforces the two-step token flow but adds no new parameter-level detail beyond what the schema already provides, so the baseline of 3 is appropriate.

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 uses a specific verb and resource ('Adds one account to one group') and clearly differentiates it from update_user by calling it 'the additive counterpart to update_user's groups list.' An agent can immediately tell this tool from its siblings, including unassign_user_from_group.

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 gives clear context for when to use this tool: adding a single user to a single group while preserving existing memberships. It names update_user as an alternative and explains the confirmation-token prerequisite. It does not explicitly state 'do not use this when...' or mention unassign_user_from_group, so it misses the top tier.

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