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

Goes well beyond the annotations: states pricing and billing mechanics ($0.80/hr, per-minute, $10 packs, 1-10 packs, never expires), the idempotency contract ('reuse request_key after a lost response; use a new one for a new purchase'), platform-specific open commands, and an explicit safety rule ('never enter payment details yourself'). This is exactly the extra behavioral context annotations cannot carry.

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 action and then packed with genuinely load-bearing facts (price, pack sizing, workflow, shell commands, retry rule); no filler sentences, though it is on the dense side with several clauses chained together.

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?

An output schema exists so return values need not be described, yet the description still tells the agent what to do with the returned url and how the operation fits between get_mac_credits, start_mac, and payment. Nothing needed to call it correctly is missing.

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%, so the baseline is 3; the description adds economic meaning to the 'packs' parameter ('$10 packs (12.5 hours each), 1 to 10 packs per purchase, and never expires') that helps an agent size the request, and reinforces the request_key retry semantics beyond the schema wording.

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 ('Get a payment link for Mac credit') plus its intended recipient ('for the human to open'), which distinguishes it from the generic sibling get_checkout_link and from read-only credit tools like get_mac_credits.

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 explicit trigger conditions ('when get_mac_credits shows too little credit or start_mac returns insufficient_credit') and names the alternatives by name, then lays out the follow-up sequence (give url, poll get_mac_credits, then start the Mac). When-to-use and what-to-do-next are both fully specified.

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