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

Annotations already cover the safety profile (readOnly, non-destructive, closed-world), and the description adds real behavioral context: values are exact-match keys, not merchant paraphrases; `complete: false` signals no published list; and empty values are not evidence of absence. That is substantive beyond the annotations, though auth, rate limits and ordering behavior are left to the schema.

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?

Three tight sentences, front-loaded with the core content ('the values the store actually uses') before the search_products relationship and the caveat. The opening noun fragment is slightly clipped but costs nothing.

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 an output schema present the description needn't explain return shape, and with full schema coverage it needn't repeat parameter docs; what remains — why the values matter and how to read `complete: false` — is covered. Nothing critical for correct invocation is missing.

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 all four parameters are already documented, and the description adds no per-parameter detail for `limit`, `fields`, `source` or `collectionId`. It does explain the semantics of the `scoped`/`complete` flags at a conceptual level, but the baseline of 3 is the correct ceiling here.

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 states exactly what is returned — the vendor, productType and tags values the store actually uses — and ties that directly to search_products' exact-match filters, which distinguishes it from the sibling that consumes these values. It never states an explicit verb (the 'List' framing only appears in the title), so it falls just short of a textbook verb+resource statement.

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?

It implicitly but clearly positions the tool as the prerequisite to search_products: 'these are the values its filters take' tells the agent to come here before filtering. It also gives a when-not-to-trust rule via the `complete: false` caveat. No explicit 'do not use this for X' exclusion is offered.

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