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

Annotations cover the safety profile (readOnlyHint=true, openWorldHint=true), and the description adds substantial context beyond them: the pricing model ($0.002 USDC per successful call via x402), the fact that failed calls are not charged, and the data attribution (TED, EU open data). This payment/charging behavior is genuinely valuable and not derivable from annotations.

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-loaded with purpose and returned fields, then param detail, then attribution and price. Every sentence carries information, though the price/attribution tail makes it slightly dense. No wasted filler.

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 an output schema present, return values need not be explained, yet the description still lists key fields helpfully. It covers source, filtering, ordering, param format, pricing, and attribution, leaving little an agent would need before calling.

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 both parameters are already documented. The description reinforces 'country is an ISO alpha-3 code (DEU, FRA, POL)', which duplicates the schema's 'e.g. DEU' and adds only extra examples, and 'matching words' lightly rephrases the 'Keywords' param. Baseline 3 is appropriate.

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 and resource ('Active EU public tenders from TED'), names the source (TED), and enumerates the returned fields plus ordering ('newest first'). An agent can immediately tell this apart from the many crypto/data siblings and understand exactly what it returns.

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 phrase 'matching words, optionally for one buyer country' implies the retrieval use case and clarifies that the country filter is optional, but there is no explicit when-to-use/when-not guidance or alternative routing. For a fairly unique tool with no close sibling, implied usage is adequate but not rich.

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