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

Beyond readOnly/openWorld annotations, the description discloses substantial behavior: per-source data provenance (Shopee Open API, AliExpress Affiliate API, public Kabum/Magalu catalog, public product page elsewhere), the degraded fallback when no credential is set (affiliate_url and final_url null, monetized:false), Amazon's credential preconditions, and where price history comes from. The harbor is that it doesn't state error behavior for unsupported URLs, but the behavioral context is otherwise rich.

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?

A single dense paragraph, and the operative constraint (URL-based lookup) is front-loaded, but a large share of the text enumerates return fields that the output schema already defines. The semicolon-clause listing of optional fields per store makes it heavier than it needs to be.

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 read-only detail tool with an output schema and only one required parameter, the description covers source-specific behavior, credential preconditions, and degraded modes, which is close to complete. It omits what happens with an unsupported or invalid product URL, which is the one remaining gap an agent would want.

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 both parameters (url and history_limit) are already documented in the schema; baseline 3 applies. The description only alludes to the price-history field's existence implicitly through the returned data list and adds no format or usage meaning 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 names a specific verb and resource ('Dados de um produto a partir da URL') and enumerates the returned fields, so an agent can tell this is a single-product detail lookup. It does not explicitly contrast with sibling tools like search_products or convert_links, so it falls short of the 5 bar for sibling differentiation.

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 by the URL-based input and the per-store notes, and useful context is given (Kabum/Magalu work without credentials; Amazon requires a Credential ID/Secret). However, it never states when to use this instead of search_products, nor what happens for unsupported URLs, so the when-to-use guidance remains implicit.

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