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

Annotations already declare readOnlyHint=true, destructiveHint=false, and openWorldHint=false, so safety and scope are covered. The description adds the output dimensions (source/medium, sessions, users, conversions), but since an output schema exists, this is supplementary rather than essential behavioral context.

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 front-loaded with the core purpose and then gives useful query examples. It is reasonably efficient, though the quoted query phrases are somewhat repetitive and the '[DEMO SINTÉTICA]' marker, while likely metadata, takes up front space.

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?

Given a simple one-parameter read tool with a full output schema and clear annotations, the description covers what the tool returns and when to use it. It does not need to re-explain safety or parameter details, and the remaining gaps are minor.

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%: the single date_range parameter is fully documented with examples and a default. The description does not mention the parameter at all, so it adds no meaning beyond the schema, making the baseline 3 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 specifically what the tool returns: traffic sources grouped by source/medium with sessions, users, and conversions. This distinguishes it from page-level siblings like list_analytics_pages, but it does not explicitly name alternatives or clarify when to use this versus get_analytics_summary.

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?

Provides clear usage context by listing example questions it answers ('de dónde viene el tráfico', 'fuentes de tráfico', 'canales de adquisición', etc.). It does not explicitly state when NOT to use it or name sibling alternatives, so it falls short of the top score.

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