add_list_member

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

With no annotations, the description carries the full burden of behavioral transparency. It only states the action and the exclusivity constraint, but does not disclose side effects, required permissions, idempotency, or error behavior (e.g., if the user is already a member). This is a significant gap for a mutating tool.

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 concise and front-loaded, with the action in the first sentence, followed by a critical usage constraint, and then a clear, structured 'Args' list. Every sentence adds value with no redundancy.

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 simple 3-parameter tool, the description covers the purpose, the necessary constraint, and each parameter's meaning. Since an output schema exists, return value documentation is not required. Minor missing context includes when to use alternative list-member tools, but overall the description is adequately complete for the tool's simplicity.

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?

The schema has no descriptions (0% coverage), so the description's parameter explanations are vital. It clearly specifies that 'list_id' is required, 'screen_name' is a Twitter username without '@', and 'user_id' is numeric. It also conveys the critical rule that exactly one of screen_name/user_id must be provided, which is not obvious from 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?

The description clearly states 'Add a user to a Twitter List' with a specific verb and resource. It distinguishes itself from sibling tools like remove_list_member and get_list_members by indicating a write/add operation.

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 an important usage constraint: 'Caller must provide exactly one of screen_name / user_id.' However, it does not explicitly mention when to use this tool versus alternatives (e.g., remove_list_member for removal or get_list_members for viewing). The usage is implied rather than stated.

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