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

Annotations only cover readOnly and openWorld; the description adds genuinely non-obvious behavior: results under a day old are cached/reused and fresh checks are capped at 10/day anonymous and 50/day signed in. That rate-limit detail is exactly the kind of operational constraint annotations cannot express, though it does not say what happens when the cap is hit.

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?

Outputs are front-loaded in the first clause, and the parenthetical tool list, while long, adds real coverage information. Two sentences with little waste; the enumeration of third-party vendors could be trimmed without loss.

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 carries the burden of describing return contents and does so concretely, and it covers the negative-result case plus caching and quota limits. The only meaningful gap is the absence of any cross-reference to the sibling tools that could equally serve a domain-lookup intent.

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?

There is a single `domain` parameter with 100% schema coverage that already documents that a URL works. The description restates 'for a domain' without adding format, normalization, or subdomain handling details, so it sits at the baseline set by the fully-documented 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?

Names a specific verb+resource (check a store by domain) and then enumerates exactly what is returned: platform, catalog size, price range, store age, and homepage tracking pixels. It even handles the negative case ('or not a store'), so an agent knows the tool is a classifier as well as an inspector, distinguishing it from lookup_brand/search_signals.

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 only implied — the agent can infer it applies when it has a domain and wants store/ecommerce intel, but the description never explicitly contrasts with siblings like lookup_brand or search_signals, nor states when it is the wrong choice. The rate-limit sentence hints at a cost consideration but not a selection rule.

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