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

Annotations already declare readOnlyHint=true, idempotentHint=true, and destructiveHint=false, so the safety profile is clear. The description adds useful behavioral context: the data source (Eurostat SDMX 2.1 API), the dataset name (demo_find), the time coverage (2018-present), update frequency (annual), and licensing (CC BY 4.0, no auth required). This goes beyond the annotations to tell the agent what to expect.

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 description is a single dense paragraph that front-loads the core purpose and then provides supporting details. It's efficient with no wasted words, though it could be slightly more structured with line breaks. Every sentence adds value: what it retrieves, from where, what indicators, what parameters, time range, and licensing.

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?

The description is complete for a read-only data retrieval tool. It covers the data source, dataset, indicators, country codes, time range, update frequency, and licensing. The output schema exists, so return values don't need to be described. The only minor gap is not explaining the default indicator behavior (TOTFERRT) in the description, though the schema covers it.

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 the schema already documents all three parameters thoroughly. The description adds context about the country parameter accepting ISO codes and EU aggregates, which mirrors the schema. The indicator enum values are explained in the schema, and the description lists them too. The description doesn't add significant meaning beyond the schema, but the schema is already complete.

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 clearly states the tool retrieves annual fertility and demographic indicators from Eurostat's SDMX 2.1 API, names the specific dataset (demo_find), and enumerates the exact indicators included. It distinguishes itself from sibling tools like eurostat2.employment.youth and eurostat2.energy.renewable by focusing on fertility/demographics.

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 description provides clear context on what data is available, the country codes accepted, and the time range. It doesn't explicitly state when to use this tool versus alternatives, but the specificity of fertility indicators makes the use case clear. It also notes the data is updated annually and covers 2018-present, which helps an agent decide if this is the right source.

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