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

No annotations are supplied, so the description carries the full burden, and it does substantial work: it declares no wallet and no signature are needed (auth/prerequisite), warns that a search "spends a paid provider call" (cost), and notes that REST pagination and degraded-source metadata come back unchanged. What it omits is the shape of the result items themselves, which matters with no output 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?

Front-loaded with the core action and the source list, then proceeds to prerequisites, filter wiring, and alternatives in a sensible order. It is dense and jargon-heavy ("engineParam", "shoprs", "ebayAspectFilter") and the raw endpoint line adds little, but no sentence is truly wasted.

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 15-parameter, zero-annotation, no-output-schema tool the description covers the highest-risk items well: auth, cost, filter provenance, and pagination passthrough. It remains incomplete on return-value structure and on roughly half the parameters, which an agent would have to infer from names alone.

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?

Coverage is only 27% across 15 parameters, so the description must compensate, and it partially does: it explains that a brands[].engineParam from get_category belongs in engineParam (sent as the eBay aspect filter) and that shoprs holds a Google filter option. However, sort, limit, page, the price/rating filters, freeShipping, and the three ebay* parameters get no semantic treatment, leaving most of the surface to name inference.

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 ("Search products across the marketplaces") and enumerates the exact searchable sources plus the "all" option, so the agent knows the reach of the call. The closing sentence distinguishes it from list_categories/get_category, which narrow rather than guess.

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?

Explicitly says when to prefer the alternatives: "when you know roughly what department a thing is in, list_categories and get_category narrow further for less." It also flags the cost of using this tool versus those. It does not address other siblings like get_deals or get_prices, so it stops short of a full routing matrix.

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