list_users

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

With no annotations, the description fully discloses that it returns a single page with no pagination, auto-resolves account_id, and details the return structure. No mention of authentication or rate limits, but those are common and implied.

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 args and returns sections. It is slightly verbose due to the full return specification, but every sentence adds value and it is front-loaded with the main purpose.

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's simplicity (one optional param, read-only), the description covers all necessary context: purpose, limitation, parameter behavior, and return format. There is no output schema provided, but the description details the return.

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 single parameter is explained in the description, including its purpose (CallRail account ID) and that it auto-resolves if omitted. This adds significant meaning beyond the schema, which has no descriptions.

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 it lists all users on an account, specifying the action and resource. It distinguishes from sibling tools like get_user and create_user by implying scope and listing behavior.

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?

Mentions the single-page limitation and that it fits small/medium accounts, providing context for when it's appropriate. Lacks explicit when-not-to-use or alternatives, but the limitation itself guides usage.

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