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

Annotations only cover readOnlyHint and openWorldHint; the description adds genuinely new behavioral facts — the $0.01 USDC charge, that a no-match returns an error with no charge, and that history is sampled daily over 30 days. That billing-on-failure rule is exactly the kind of detail an agent needs before calling. It does not discuss rate limits, pagination behavior with limit, or latency. One tension: openWorldHint=false sits awkwardly with live searching of 180+ third-party stores, though this reads as an annotation imprecision rather than a direct contradiction of the text.

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-loads the cost signal ("PAID $0.01 USDC") and then the capability, with zero filler sentences. Dense field enumeration makes it slightly list-heavy, but every clause carries information an agent can act on.

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?

There is no output schema, and the description compensates by naming the returned fields and the error path. Payment and auth are handled in the schema. Remaining gaps are minor: how limit affects result shape and whether results are ranked.

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 every parameter already has its own description and the baseline is 3. The description only echoes the optional domain filter and says nothing about limit (1-50) or how api_key interacts with the x402 payment path beyond the schema's own wording, so it adds little meaning.

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 Shopify brand stores by product name or SKU — and enumerates the returned fields (price, compare-at, discount %, stock flag, URL, image, 30-day history). This is far more specific than a name restatement. It stops short of a 5 because it never distinguishes itself from near-identical siblings such as free_ecom, ecom_catalog, or ecom_snapshot.

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 scope (product/keyword/SKU search across 180+ stores). However, with four ecom_* siblings plus free_ecom in the toolset, the description gives no when-to-use or when-not-to-use guidance, and no indication of how this differs from the free or catalog variants.

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