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

Annotations already declare the tool is a safe, idempotent read (readOnlyHint, idempotentHint, openWorldHint=false), so the description's job is to add behavior beyond that. It does: truncation semantics (returns the most recent points if the range exceeds max_puntos, default 104, max 520), the linked CSV for the full series, and the warning that points are figures, not time units, because out-of-season periods have no price.

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 key scoping facts (date range, coverage since 2017/2019/2005, truncation behavior) are front-loaded and each clause carries information. The trailing Spanish restatement ('— La serie de precios entre dos fechas') is redundant padding that duplicates the opening sentence.

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?

With no output schema, the description must convey the return shape, and it does: points are figures, truncated to max_puntos most-recent, full data in the linked CSV. What remains missing is guidance on how to obtain a valid serie value and when this tool is preferable to its siblings.

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 coverage is 100%, so the baseline is 3; the description however adds genuine meaning beyond the schema — it clarifies that returned points are figures rather than weekly/daily entries, and restates the truncation rule and default 104/max 520 in context. It does not explain the serie identifier format beyond pointing to buscar_producto.

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 verb and resource: 'Price series of an identifier between two dates', and adds concrete coverage windows (weekly since 2017 for Valencia, daily since October 2026 for diesel). It does not explicitly distinguish itself from siblings like the schema's reference to buscar_producto (for obtaining the identifier) or precio_ultimo/plazos, so sibling differentiation is implied rather than stated.

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 gives real usage guidance for parameters ('for a period, use desde and hasta'), which tells the agent how to request a range. However, it never says when to choose this tool over precio_ultimo or plazos, nor any prerequisite such as first calling buscar_producto to obtain the serie (that hint lives only in the schema).

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