sw_add_user_to_group

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

With no annotations provided, the description carries the behavioral burden, and it does so well by disclosing the confirmation requirement, distinguishing the elicitation prompt path from the two-step confirmToken fallback, and explicitly stating that only a repeat call with that token proceeds. It does not cover permissions, error cases, or the final success response, but the confirmation behavior is a significant and unusual trait that is clearly communicated.

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 compact and front-loaded with the core action, then the parameter strategies, then the confirmation flow. Every sentence adds useful information and there is no filler. The confirmation logic is complex enough to warrant the longer sentences, though the parenthetical MCP_CONFIRM_MODE reference adds a slight readability tax.

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 mutating tool with six parameters, no annotations, and no output schema, the description covers the identification modes, the confirmation requirement, and the token fallback in enough detail for an agent to invoke it correctly. It does not describe the final success response, error conditions, or parameter validation rules, but the core operational context is present.

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 coverage is only 50%, and the description compensates by adding meaningful parameter semantics: user_id is preferred and can be resolved via sw_list_friends, and first_name + last_name + email form an explicit invite-by-email combination. The confirmToken semantics are already well-documented in the schema, and the description reinforces the 'never on the first call' rule. Minor validation constraints, such as whether email is required with name fields, are not covered.

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 opens with a specific verb and resource: 'Add a user to a Splitwise group.' It also names both supported invocation modes (user_id versus first_name + last_name + email), which gives an agent a precise picture of the operation and clearly distinguishes it from sibling tools like sw_remove_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?

It gives explicit guidance on when each input strategy should be used: prefer user_id, resolve a name via sw_list_friends, or invite by email with first/last name and email. It also explains the confirmation flow and the token fallback. It does not explicitly state when not to use the tool versus related sibling mutations, so it falls just short of a 5.

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