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

Annotations already declare readOnly/idempotent/non-destructive/closed-world, so the safety profile is covered. The description still adds real value beyond them: it explicitly says no stock is reserved and that shipping, destination taxes and discounts are excluded from the estimate and deferred to checkout — the key behavioral caveat about what the returned total does and does not include.

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 tight sentences: the core action first, then the critical exclusions. Every clause carries information and nothing is padded or buried.

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?

An output schema exists, so return values need not be explained, and annotations cover safety. For a single-parameter read-only estimator, the description supplies the main missing context (no reservation, totals partial), leaving only item-level input semantics unaddressed.

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% for the single required 'items' parameter, a nested array whose product_id/quantity fields carry no prose. The description only says 'una selección… de productos', restating the parameter name; it says nothing about the 1–20 item cap, the 1–20 quantity bounds, or how invalid/unavailable products are reported.

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 pair of actions on a specific resource: 'Comprueba una selección y estima su importe de productos' — validate a selection and estimate its total. That distinguishes it from get_product/search_products (lookup) and implicitly from prepare_checkout, though it never names a sibling explicitly.

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?

Usage is implied rather than stated: the note that stock is not reserved and that shipping/taxes/discounts are computed 'en el checkout' signals this is a pre-checkout estimator. There is no explicit 'use this when…' or 'use prepare_checkout instead when…' clause, so the agent must infer the boundary.

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