Extend a machine

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

Annotations already declare readOnlyHint=false and openWorldHint=true, but the description adds the critical non-obvious fact that the call costs money and requires a quote/confirm dance. That is genuine value beyond structured data; only return-format/pagination style details are absent, and an output schema exists.

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?

Two short sentences, front-loaded with the cost warning and the quote-first instruction. 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 paid mutation tool with an output schema present, the description covers purpose, cost, and the approval flow adequately. Minor gap: no mention of what happens on failure or whether the quote expires, but nothing blocking correct invocation.

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 75% and already documents confirm and expected_total_usd, but the description reinforces their interlocking semantics ('the quoted total_usd' tied to confirm=true). It adds real workflow meaning over the field descriptions rather than repeating them.

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 ('Add time') and resource ('a machine') plus a pricing constraint ('at the price it launched with'). Clearly distinguishable from siblings like launch_machine and stop_machine.

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 a two-step workflow: quote with confirm=false first, then confirm=true with expected_total_usd after the person agrees. Strong usage context, though it doesn't name sibling alternatives or when-not-to-extend conditions.

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