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

With no annotations, the description carries the full burden and does disclose useful traits: read-only, free for cached items (implying non-cached may incur cost), and the marketplace data sources and currency. It stops short of stating latency, rate limits, or what happens for uncached items, leaving a gap for a mutation-free but potentially costly lookup.

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?

One dense sentence plus a short example; the purpose and return shape are front-loaded with no filler. Minor run-on structure but every clause (sources, currency, cost, example) earns its place.

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 single-param lookup with no output schema, the description covers purpose, returned fields, data provenance, currency, and cost model. It omits edge-case behavior (no data found, uncached pricing), which is the only meaningful remaining gap.

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% with a single, well-described 'q' parameter, so the baseline is 3. The description adds a concrete good-query example ('used playstation 5 console'), which demonstrates the expected natural-language item format beyond the terse schema hint.

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+resource ('current second-hand value check') and enumerates the return shape (low/typical/high price plus confidence) and data sources (eBay/Discogs in GBP). This is clear and distinct from get_history/get_sold, though it never names those siblings explicitly to sharpen the contrast.

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 for a current second-hand value check' gives an explicit trigger, and 'current' implicitly frames it against the historical siblings. However, no alternatives or when-not-to-use conditions are stated, so the agent still infers routing against check_deal/get_history/get_sold.

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