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

Annotations already declare readOnlyHint=true and openWorldHint=false, so the safety profile is known. The description adds meaningful context beyond that — a fixed cost of 5 prepaid credits and a production billing requirement — which is genuinely useful for an agent deciding whether to call it. It still omits the computation formula and whether the result is a count or a percentage.

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 core operation before the billing caveat. No filler, though the pricing sentence could be tightened into a single clause.

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?

The tool has three undocumented required parameters and no output schema, so the description should explain what is returned (a failure count, a percentage, whether it can go negative) and what the inputs mean. Neither is covered, leaving the agent unable to call it confidently beyond guessing from parameter names.

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 0% for all three parameters (requests, failed, slo_pct), so the description must compensate — but it only vaguely implies 'supplied SLO' and 'remaining failures'. It never clarifies units, whether requests/failed are counts over a window, or whether slo_pct is 0-1 or 0-100.

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 ('Compute') and a specific output ('remaining failures allowed') scoped to a supplied SLO, which an agent can distinguish from generic budget tools. It does not explicitly name or contrast with the closest sibling (privi_slo_budget), so differentiation relies on inference.

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?

The only guidance is billing ('PAID ONLY: 5 prepaid credits; production billing required'). There is no statement of when to use this versus privi_slo_budget, privi_rate_budget, or privi_timeout_budget, nor any prerequisite conditions beyond payment.

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