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 useful behavioral context: it names the underlying data source (servicios.ine.es, INE Tempus3 API) and explicitly states 'no auth required', which is valuable operational information beyond the annotations. It doesn't describe rate limits or response format, but the output schema exists and the read-only nature is well covered.

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 with zero waste. The first sentence states the action, resource, and return fields. The second sentence provides the data source and auth status. Every clause earns its place, and the most important information is front-loaded.

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 single-parameter read-only metadata lookup with a full output schema, the description is nearly complete. It covers what the tool returns, the data source, and auth requirements. It doesn't mention rate limits or pagination, but for a metadata lookup with one parameter and an output schema, these are minor gaps. The example series_code further anchors the expected input.

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 the single parameter. The description adds a concrete example ('IPC206449' for the national CPI monthly change series), which helps an agent understand the expected format. With only one parameter and full schema coverage, the description's example is a meaningful addition beyond the schema.

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 verb ('Get metadata'), a specific resource ('Spanish INE time series by its series_code'), and enumerates the exact fields returned (name, decimals, periodicity, parent operation, publication). It also names the data source and auth requirement, which distinguishes it from sibling tools like ine.series.data (which fetches data) and ine.reference.operations (which lists operations).

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 clearly implies when to use this tool: when you need metadata for a specific series_code, not the data itself. It doesn't explicitly name sibling alternatives or state when NOT to use it, but the context of sibling tools (ine.series.data, ine.reference.operations, ine.reference.tables) makes the usage context clear. The example series_code also provides practical guidance.

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