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

Beyond the annotations (readOnly, idempotent, non-destructive, open-world) the description discloses payment mechanics, that invalid input is refused pre-payment, that failed runs are never charged, and that an unpaid call returns PaymentRequired. It also states non-obvious aggregation semantics: amounts are never summed across currencies and value-less notices are counted as missing. This is exactly the behavioral context annotations cannot convey.

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?

The purpose and return shape are front-loaded, then payment/pricing, then call mechanics. It is dense and long, but nearly every clause carries information; the appended HTTP URL example is the one element that could be trimmed without loss.

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 fully carries the return-shape burden: per-award fields, aggregate stats per currency, edge-case handling for missing values, and the payment-failure response. An agent has everything needed to call it and interpret results.

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 all nine parameters are already documented with examples (country ISO codes, CPV 2-8 digits, limit 1-50, date formats). The description only echoes the filter concepts and adds no syntax, defaults, or interaction rules beyond the schema, so the baseline 3 applies.

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?

The description states a specific resource (published contract award results) and the exact filter axes (supplier, buyer, country, CPV, date range), then enumerates what each record contains (winners, values, currency, dates, buyer) plus an aggregate block. An agent can immediately tell this returns awards rather than notices, though it never names the sibling it differs from (e.g. tenders_search for notices, tenders_get_supplier_history).

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?

It gives clear operational context: filters that drive selection, price of 0.02 USDC, x402 payment rails, no account/API key, invalid input refused before payment, and pointing to get_example for call syntax. What is missing is explicit routing guidance ('use tenders_search instead when you want open notices'), so there is context but no exclusions.

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