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

Annotations already declare readOnlyHint, idempotentHint, openWorldHint and destructiveHint=false, so the safety profile is covered. The description adds real context beyond that by declaring the returned content authoritative and describing the bulk-vs-paginated distinction. It doesn't state cost, rate limits, or latency for the remote lookup, which keeps it below a 5.

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?

Two sentences, front-loaded with what the tool returns, followed by the routing guidance. Every clause carries distinct information with no restatement of the 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?

There is no output schema, so the description compensates by enumerating the return payload fields directly (URL, row count, snapshot dates, country values). For a zero-parameter metadata tool that is sufficient for an agent to call it correctly and to know what will come back.

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?

The tool takes zero parameters, so there is nothing for the description to disambiguate; baseline is 4. The description correctly avoids inventing parameter-like filters and instead explains the one input-free choice (bulk file vs paginated search).

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 resource (dataset metadata) and enumerates exactly what it returns: bulk-download URL, row count, snapshot dates, and the distinct country value list. It also names the sibling tool it precedes (ema_article57_search), so an agent can separate it from the search sibling without opening either schema.

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 says when to call it: 'Use this before ema_article57_search when you need the exact country spelling or want the bulk file instead of paginated rows.' That gives both the trigger condition and the alternative it substitutes for.

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