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

Annotations already mark the tool read-only and open-world, but the description adds substantial behavioral detail: it defines the substitute list's composition (up to 5, same kind, same price band, brief record fields) and what triggers it. No contradiction with the readOnlyHint/openWorldHint 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?

Two sentences: the first establishes the core purpose up front, the second handles the only edge case an agent needs to know. There is no filler or repetition of schema content.

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 is the sole source for the return shape and it covers the main fields, the substitution behavior, and the complete record layout for alternatives. The tool is simple enough that an agent can invoke it correctly with the given information.

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% for both parameters, so the schema already documents product_id and language. The description adds only a slight tie-in via 'localized price' but does not need to compensate for a coverage gap.

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?

Description opens with a concrete action-resource pair ('Get full details for one product by id') and enumerates the payload (description, specs, stock, VAT-included localized price). The closing instruction 'offer them instead of searching' clearly separates this single-item lookup from the search_products sibling.

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 makes the primary use case explicit (fetching one product by id) and gives a clear conditional: when the product is out of stock, surface substitutes rather than searching. It does not explicitly name search_products as the alternative, but the directive is unambiguous.

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