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

Annotations already cover the safety profile (readOnly, idempotent, non-destructive, closed-world), so the description's added value is the fee model it assumes (eBay US fees by default), the currency matching requirement, and the verdict categories returned. It does not state whether the verdict has thresholds or tolerances, which would have been useful.

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-loads the output (net proceeds + verdict) before the input mechanics and the currency caveat. Four sentences, all bearing load, though the currency/eBay UK explanation is dense enough that it could be tightened slightly.

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 carries the return-value burden and does describe the two returned concepts (seller net, verdict label). The tool's complexity is low and the currency and fee-model assumptions are stated, leaving only minor ambiguity about verdict thresholds.

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 two parameters are already documented; the baseline is 3. The description adds meaning beyond the schema by insisting both values be in the same currency and tying that currency to price_item's price.currency, which is a real constraint not captured in the schema.

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 precise computation (net proceeds after eBay fees) plus the verdict output (worth it / thin / pass) for two named inputs. It clearly distinguishes itself from price_item by describing itself as arithmetic on a known sale price rather than a price lookup.

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 routes the agent: 'Use price_item first when the sale price is unknown', and explains that the eBay UK worthIt block from price_item already applies local fees. This is a concrete when-to-use/when-to-defer rule naming the sibling tool.

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