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

Annotations already cover the safety profile (readOnlyHint=true, openWorldHint=false), and the description still adds real value: the comparison is over "every tracked provider's current list price" (consistently a closed tracked dataset) and it discloses quota and billing — 50 free calls/day then $0.01 USDC on Base via x402. That cost/quota disclosure is exactly the kind of context annotations can't carry. It stops short of describing freshness/staleness of prices or tie-breaking behavior.

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?

Three short sentences: trigger first, mechanism and return value second, cost model last. Every sentence carries distinct information and nothing is repeated from the schema or title.

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?

With no output schema, the description correctly notes what comes back ("the cheapest with its source"). For a 3-parameter read-only lookup with full schema coverage, the only remaining gap is whether results reflect live or cached pricing and what happens when no provider matches the region.

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 all three parameters including the price_type enum and its default are already documented in the schema. The description's only added semantics is "optionally in one region," which restates the region parameter without adding format or edge-case detail. Baseline 3 is appropriate when the schema does the heavy lifting.

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?

"Compares every tracked provider's current list price per GPU-hour, and returns the cheapest with its source" states a specific verb (compare/find cheapest) and resource (GPU-hour rental price), which separates it from price-listing siblings like compute_list_prices and get-gpu-price. It never names those siblings explicitly, so the differentiation is implied by the superlative "cheapest" rather than spelled out.

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?

"Use when you need the cheapest place to rent a given GPU" gives a clear triggering condition and the optional-region narrowing is stated. There is no when-not guidance and no explicit pointer to alternative tools, so an agent comparing against get-gpu-price or compute_list_prices must infer the boundary itself.

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