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 covered. The description adds that the tool returns period, unit, and attribution, and that it costs 0.01 USD per call with x402. It does not disclose what happens if the serie is invalid or not found, or how the attribution requirement affects the response. The pricing disclosure is a useful behavioral addition beyond 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?

The description is two sentences and front-loads the core function. The pricing sentence is arguably necessary for a paid tool. It is concise and every sentence adds information, though the pricing could be seen as secondary.

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?

For a tool with one undocumented parameter, no output schema, and no usage guidance, the description is incomplete. An agent cannot reliably construct a valid 'serie' value from the description alone. The openWorldHint suggests the parameter accepts open-world values, but the description does not provide examples of valid serie identifiers or how to discover them. The pricing and attribution info are useful, but the core calling contract is underspecified.

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 0% and the only parameter 'serie' has an empty schema with no description. The description mentions example series (IPC, paro, población) but does not explain what format the serie parameter should take (e.g., INE series code, name, URL). With 0% coverage and no parameter documentation, the description must compensate, and it only partially does by giving examples of series topics.

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 returns the latest published value of an INE series, with period, unit, and attribution. It names example series (IPC, unemployment, population), which helps an agent understand the resource. It doesn't explicitly distinguish itself from the sibling indicador-eurostat, but the INE vs Eurostat distinction is implicit in the name and description.

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 implies when to use it: when you need the latest INE data point. It does not explicitly state when not to use it or mention the sibling indicador-eurostat as the alternative for Eurostat data. The pricing note is context but not usage guidance. The lack of required parameters and openWorldHint suggest the agent may need to discover the serie parameter, but no guidance is given on how to find valid series identifiers.

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