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

Beyond the annotations it discloses non-obvious behavior: the result is a cached ARC check up to 24 hours old, no login/model call/payment/browser scan occurs, a missing result means unknown rather than 'no', a checkout link means reachable checkout not a completed order, and output is advisory with ARC stopping before payment. These are exactly the interpretive caveats an agent needs and none are recoverable from readOnlyHint/openWorldHint/idempotentHint.

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?

The invocation condition is front-loaded in the first sentence and every subsequent sentence adds a distinct fact (what the payload contains, what it does not do, cache freshness, interpretation caveats). It is dense and the first sentence is a comma-heavy run-on, but there is no filler to cut.

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 one required param, full annotations, and no output schema, the definition still describes the returned fields (catalog, product, checkout link, UCP profile, blocks, fix) and explains how to read a null result. Nothing an agent needs in order to call it correctly or interpret the response 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% and the single parameter's description already says 'Public store homepage or product URL', so the schema carries most of the load. The description adds real value by clarifying the URL may be any public store, not only Index brands, which prevents an agent from withholding a valid URL; it does not explain malformed-URL handling or homepage-vs-product differences.

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 definition names a specific operation (saved HTTP checkout-link check) and resource (a public store homepage or product URL), and enumerates what the result contains: catalog, product, checkout link, UCP profile, blocks, and one fix. It even scopes itself against a narrower variant ('not only Index brands'), though it never names siblings like google_checkout_readiness or precheck, so sibling disambiguation is only partial.

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 gives explicit trigger conditions in natural-language form ('Call when you need...', 'what stops an agent at <store> checkout?', 'which checkout route works on <store>?'), which is strong positive guidance. It lacks any explicit when-not or named-alternative routing (e.g. 'use google_checkout_readiness instead for X'), so an agent must infer the boundary from the sibling list.

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