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

Annotations already flag destructiveHint=true and non-idempotent, but the description adds the crucial economic and physical consequences: postage and printing are charged to either prepaid credit or invoice, and real mail goes to every recipient. It further discloses the irreversibility nuance beyond the flat destructive flag — Invoice jobs can be cancelled pre-processing, User Credit jobs cannot.

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?

Front-loaded with the risk warning, then purpose, then preconditions, then cancellation limits, then endpoint. Every sentence carries operational weight, and the repeated confirm reminder earns its place as a safety-critical gate rather than 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 three-parameter, high-consequence mutation with full schema coverage and no output schema, the description supplies everything an agent needs: cost implications, approval protocol, irreversibility conditions, and billing-mode consequences. Nothing material is left to inference.

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% and all three parameters are documented, including the billing_type enum semantics and the confirm const constraint. The description restates '`confirm` must be true' but adds no new syntax or format detail beyond the schema, so the 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 ('submit a draft job for printing and USPS mailing') and immediately distinguishes it from sibling creation/read tools like click2mail_create_job, get_job_cost and get_job_status. The lead-in 'WRITE, SPENDS MONEY, NOT REVERSIBLE' makes the operation class unambiguous at a glance.

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?

Explicitly prescribes prerequisites ('read click2mail_get_job_cost and click2mail_get_credit') and the approval gate ('get the user's explicit go-ahead for this job and amount', '`confirm` must be true'). It also states the cancellation boundary (Invoice only, before processing), which tells the agent when this action cannot be undone.

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