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

Annotations declare the write/destructive profile, and the description adds substantial context beyond them: a preview-first two-step flow gated on confirm=true, the assurance that no money moves, and the fact that only a payment request is sent via Appty. This is exactly the behavioral detail an agent needs before calling a destructive 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?

Four short sentences, each carrying a distinct fact: what is sent, the preview gate, the no-money-movement assurance, and the exclusions. Front-loaded with purpose and no filler.

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 no output schema, the description covers purpose, confirmation workflow, scope limits, and side effects. It does not describe what the preview contains, but that is a minor gap given the annotations and full schema coverage.

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 schema already documents confirm, client_id, and booking_id in detail. The description reinforces the confirm=true gating and the either/or parameter choice but adds no syntax or format detail beyond what the schema provides. Baseline 3 applies.

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?

States a specific verb and resource ('Email a pay link') and enumerates the two targeting modes (one booking, or a client's unpaid sessions and invoices). An agent can distinguish this from siblings like send_invoice or who_owes without opening any schema.

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?

Gives clear usage context (single booking vs. client-level unpaid items) and explicit exclusions ('Group spots, packages, and fees are not emailed'), which functions as when-not guidance. It stops short of naming an alternative tool such as send_invoice for the excluded cases.

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