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

With no annotations provided, the description carries the burden. It discloses the return behavior ('Returns the created or existing waitlist entries'), a prerequisite call, and a cost token amount. It does not mention side effects beyond adding, but for a simple creation tool this is reasonable. It also implies idempotency by returning existing entries.

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 four sentences, with the main action front-loaded and no padding. Each sentence earns its place: purpose, prerequisite/instance selection, return value, and cost. It is concise and well-structured.

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 low complexity (2 params, full schema descriptions, output schema present), the description covers all critical information: what it does, prerequisite, how to target an instance, return value, and cost. It lacks explicit alternatives but that is not essential for completeness here.

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 100% and both parameters have detailed descriptions. The tool description only echoes the schema's guidance for clerk_instance_id and provides no new meaning for waitlist_entries beyond what the schema already states. Therefore, it adds no value beyond the baseline.

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 one or more email addresses to the waitlist in a connected Clerk application.' This clearly distinguishes the tool from sibling tools like list_waitlist_entries, invite_waitlist_entry, reject_waitlist_entry, and delete_waitlist_entry by focusing on creation/addition.

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 provides explicit usage guidance: 'Call clerk.get_connected_accounts first' and 'Pass clerk_instance_id to target a specific connection, or omit it to use the default account.' This gives clear context on prerequisites and parameter selection, though it does not explicitly name alternatives or when-not-to-use cases.

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